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/path/join.rs

@@ -32,7 +32,11 @@ impl Command for SubCommand {
                 (Type::Record(vec![]), Type::String),
                 (Type::Table(vec![]), Type::List(Box::new(Type::String))),
             ])
-            .rest("append", SyntaxShape::String, "Path to append to the input")
+            .rest(
+                "append",
+                SyntaxShape::String,
+                "Path to append to the input.",
+            )
             .category(Category::Path)
     }
 

crates/nu-command/src/path/relative_to.rs

@@ -37,7 +37,7 @@ impl Command for SubCommand {
             .required(
                 "path",
                 SyntaxShape::String,
-                "Parent shared with the input path",
+                "Parent shared with the input path.",
             )
             .category(Category::Path)
     }