Enforce required, optional, and rest positional arguments start with an uppercase and end with a period. (#11285)

# Description

This updates all the positional arguments (except with
`--features=dataframe` or `--features=extra`) to start with an uppercase
letter and end with a period.

Part of #5066, specifically [this
comment](/nushell/nushell/issues/5066#issuecomment-1421528910)

Some arguments had example data removed from them because it also
appears in the examples.

There are other inconsistencies in positional arguments I noticed while
making the tests pass which I will bring up in #5066.

# User-Facing Changes

Positional arguments are now consistent

# Tests + Formatting

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

# After Submitting

Automatic documentation updates

crates/nu-command/src/help/help_.rs

@@ -28,7 +28,7 @@ impl Command for Help {
             .rest(
                 "rest",
                 SyntaxShape::String,
-                "the name of command, alias or module to get help on",
+                "The name of command, alias or module to get help on.",
             )
             .named(
                 "find",

crates/nu-command/src/help/help_aliases.rs

@@ -26,7 +26,7 @@ impl Command for HelpAliases {
             .rest(
                 "rest",
                 SyntaxShape::String,
-                "the name of alias to get help on",
+                "The name of alias to get help on.",
             )
             .named(
                 "find",

crates/nu-command/src/help/help_commands.rs

@@ -27,7 +27,7 @@ impl Command for HelpCommands {
             .rest(
                 "rest",
                 SyntaxShape::String,
-                "the name of command to get help on",
+                "The name of command to get help on.",
             )
             .named(
                 "find",

crates/nu-command/src/help/help_externs.rs

@@ -26,7 +26,7 @@ impl Command for HelpExterns {
             .rest(
                 "rest",
                 SyntaxShape::String,
-                "the name of extern to get help on",
+                "The name of extern to get help on.",
             )
             .named(
                 "find",

crates/nu-command/src/help/help_modules.rs

@@ -32,7 +32,7 @@ are also available in the current scope. Commands/aliases that were imported und
             .rest(
                 "rest",
                 SyntaxShape::String,
-                "the name of module to get help on",
+                "The name of module to get help on.",
             )
             .named(
                 "find",