Create nu_glob::is_glob function (#14717)

# Description

Adds an `is_glob` function to the nu-glob crate that takes a string
pattern and returns whether or not it's a glob that would be expanded by
nu-glob. Right now, this just means checking if it contains `*`, `?`, or
`[`.

Previously, this same code was duplicated in the following places:
- `ls`: Determining whether to read a folder's contents or expand a glob
- `run_external.rs` in nu-command: Arguments to externals only have
n-dots and tilde expansion applied if they weren't globs
- `glob_from` in nu-engine:
  - `glob_from` can get the prefix in a simpler way for non-globs
- If the canonical path for a non-glob path contains glob
metacharacters, it needs to be escaped
- `completion_common.rs` in nu-cli: File/folder completions containing
glob metacharacters need to be wrapped in quotes

All of these locations can use `nu_glob::is_glob` now instead of rolling
their own checks. This does mean that nu-cli now has a dependency on
nu-glob.

# User-Facing Changes

Users of nu-glob will now be able to check if a given pattern is a glob
expanded by nu-glob.

For users of Nushell, completion suggestions for files containing `]`
will no longer be wrapped in quotes if they contain no other glob
metacharacters. This is because unmatched `]`s are ignored by nu-glob,
but we used to consider such file completions contaminated anyway.

# Tests + Formatting

This is a very basic function, so I just added some doctests.

# After Submitting

This is meant to be used in
https://github.com/nushell/nushell/pull/14674.

crates/nu-command/src/filesystem/ls.rs

@@ -33,8 +33,6 @@ struct Args {
     call_span: Span,
 }
 
-const GLOB_CHARS: &[char] = &['*', '?', '['];
-
 impl Command for Ls {
     fn name(&self) -> &str {
         "ls"
@@ -291,7 +289,7 @@ fn ls_for_one_pattern(
                 {
                     return Ok(Value::test_nothing().into_pipeline_data());
                 }
-                just_read_dir = !(pat.item.is_expand() && pat.item.as_ref().contains(GLOB_CHARS));
+                just_read_dir = !(pat.item.is_expand() && nu_glob::is_glob(pat.item.as_ref()));
             }
 
             // it's absolute path if:

crates/nu-command/src/system/run_external.rs

@@ -340,11 +340,9 @@ fn expand_glob(
     span: Span,
     signals: &Signals,
 ) -> Result<Vec<OsString>, ShellError> {
-    const GLOB_CHARS: &[char] = &['*', '?', '['];
-
-    // For an argument that doesn't include the GLOB_CHARS, just do the `expand_tilde`
+    // For an argument that isn't a glob, just do the `expand_tilde`
     // and `expand_ndots` expansion
-    if !arg.contains(GLOB_CHARS) {
+    if !nu_glob::is_glob(arg) {
         let path = expand_ndots_safe(expand_tilde(arg));
         return Ok(vec![path.into()]);
     }