Ensure that command usage starts uppercase and ends period (#11278)

# Description

This repeats #8268 to make all command usage strings start with an
uppercase letter and end with a period per #5056

Adds a test to ensure that commands won't regress

Part of #5066

# User-Facing Changes

Command usage is now consistent

# Tests + Formatting

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting

Automatic documentation updates

crates/nu-cmd-dataframe/src/dataframe/expressions/expressions_macro.rs

@@ -319,7 +319,7 @@ macro_rules! lazy_expr_command {
 expr_command!(
     ExprList,
     "dfr implode",
-    "Aggregates a group to a Series",
+    "Aggregates a group to a Series.",
     vec![Example {
         description: "",
         example: "",
@@ -334,7 +334,7 @@ expr_command!(
 expr_command!(
     ExprAggGroups,
     "dfr agg-groups",
-    "creates an agg_groups expression",
+    "Creates an agg_groups expression.",
     vec![Example {
         description: "",
         example: "",
@@ -349,7 +349,7 @@ expr_command!(
 expr_command!(
     ExprCount,
     "dfr count",
-    "creates a count expression",
+    "Creates a count expression.",
     vec![Example {
         description: "",
         example: "",
@@ -364,7 +364,7 @@ expr_command!(
 expr_command!(
     ExprNot,
     "dfr expr-not",
-    "creates a not expression",
+    "Creates a not expression.",
     vec![Example {
         description: "Creates a not expression",
         example: "(dfr col a) > 2) | dfr expr-not",
@@ -379,7 +379,7 @@ expr_command!(
 lazy_expr_command!(
     ExprMax,
     "dfr max",
-    "Creates a max expression or aggregates columns to their max value",
+    "Creates a max expression or aggregates columns to their max value.",
     vec![
         Example {
             description: "Max value from columns in a dataframe",
@@ -424,7 +424,7 @@ lazy_expr_command!(
 lazy_expr_command!(
     ExprMin,
     "dfr min",
-    "Creates a min expression or aggregates columns to their min value",
+    "Creates a min expression or aggregates columns to their min value.",
     vec![
         Example {
             description: "Min value from columns in a dataframe",
@@ -469,7 +469,7 @@ lazy_expr_command!(
 lazy_expr_command!(
     ExprSum,
     "dfr sum",
-    "Creates a sum expression for an aggregation or aggregates columns to their sum value",
+    "Creates a sum expression for an aggregation or aggregates columns to their sum value.",
     vec![
         Example {
             description: "Sums all columns in a dataframe",
@@ -514,7 +514,7 @@ lazy_expr_command!(
 lazy_expr_command!(
     ExprMean,
     "dfr mean",
-    "Creates a mean expression for an aggregation or aggregates columns to their mean value",
+    "Creates a mean expression for an aggregation or aggregates columns to their mean value.",
     vec![
         Example {
             description: "Mean value from columns in a dataframe",
@@ -559,7 +559,7 @@ lazy_expr_command!(
 expr_command!(
     ExprMedian,
     "dfr median",
-    "Creates a median expression for an aggregation",
+    "Creates a median expression for an aggregation.",
     vec![Example {
         description: "Median aggregation for a group-by",
         example: r#"[[a b]; [one 2] [one 4] [two 1]]
@@ -590,7 +590,7 @@ expr_command!(
 lazy_expr_command!(
     ExprStd,
     "dfr std",
-    "Creates a std expression for an aggregation of std value from columns in a dataframe",
+    "Creates a std expression for an aggregation of std value from columns in a dataframe.",
     vec![
         Example {
             description: "Std value from columns in a dataframe",
@@ -636,7 +636,7 @@ lazy_expr_command!(
 lazy_expr_command!(
     ExprVar,
     "dfr var",
-    "Create a var expression for an aggregation",
+    "Create a var expression for an aggregation.",
     vec![
         Example {
             description:

crates/nu-cmd-dataframe/src/dataframe/expressions/otherwise.rs

@@ -15,7 +15,7 @@ impl Command for ExprOtherwise {
     }
 
     fn usage(&self) -> &str {
-        "completes a when expression."
+        "Completes a when expression."
     }
 
     fn signature(&self) -> Signature {

crates/nu-cmd-dataframe/src/dataframe/lazy/fetch.rs

@@ -16,7 +16,7 @@ impl Command for LazyFetch {
     }
 
     fn usage(&self) -> &str {
-        "collects the lazyframe to the selected rows."
+        "Collects the lazyframe to the selected rows."
     }
 
     fn signature(&self) -> Signature {

crates/nu-cmd-dataframe/src/dataframe/lazy/flatten.rs

@@ -17,7 +17,7 @@ impl Command for LazyFlatten {
     }
 
     fn usage(&self) -> &str {
-        "An alias for dfr explode"
+        "An alias for dfr explode."
     }
 
     fn signature(&self) -> Signature {

crates/nu-cmd-dataframe/src/dataframe/lazy/macro_commands.rs

@@ -121,7 +121,7 @@ lazy_command!(
     "dfr reverse",
     "Reverses the LazyFrame",
     vec![Example {
-        description: "Reverses the dataframe",
+        description: "Reverses the dataframe.",
         example: "[[a b]; [6 2] [4 2] [2 2]] | dfr into-df | dfr reverse",
         result: Some(
             NuDataFrame::try_from_columns(vec![
@@ -147,7 +147,7 @@ lazy_command!(
 lazy_command!(
     LazyCache,
     "dfr cache",
-    "Caches operations in a new LazyFrame",
+    "Caches operations in a new LazyFrame.",
     vec![Example {
         description: "Caches the result into a new LazyFrame",
         example: "[[a b]; [6 2] [4 2] [2 2]] | dfr into-df | dfr reverse | dfr cache",

crates/nu-cmd-dataframe/src/dataframe/lazy/sort_by_expr.rs

@@ -16,7 +16,7 @@ impl Command for LazySortBy {
     }
 
     fn usage(&self) -> &str {
-        "sorts a lazy dataframe based on expression(s)."
+        "Sorts a lazy dataframe based on expression(s)."
     }
 
     fn signature(&self) -> Signature {