complete/fish: improve shell completions for fish

- Stop using `-n __fish_use_subcommand`. This had the effect of
ignoring options if a positional argument has already been given, but
that's not how ripgrep works.

- Only suggest negation options if the option they're negating is
passed (e.g., only complete `--no-pcre2` if `--pcre2` is present). The
zsh completions already do this.

- Take into account whether an option takes an argument. If an option
is not a switch then it won't suggest further options until the
argument is given, e.g. `-C<tab>` won't suggest options but `-i<tab>`
will.

- Suggest correct arguments for options. We already completed a fixed
set of choices where available, but now we go further:

  - Filenames are only suggested for options that take filenames.

  - `--pre` and `--hostname-bin` suggest binaries from `$PATH`.

  - `-t`/`--type`/&c use `--type-list` for suggestions, like in zsh,
  with a preview of the glob patterns.

  - `--encoding` uses a hardcoded list extracted from the zsh
  completions. This has been refactored into a separate file, and the
  range globs (`{1..5}`) replaced by comma globs (`{1,2,3,4,5}`) since
  those work in both shells. I verified that this produces the same
  list as before in zsh, and the same list in fish (albeit in a
  different order).

PR #2684

CHANGELOG.md

@@ -1,3 +1,13 @@
+14.1.0 (TBD)
+============
+This is a minor release with a few small new features and bug fixes.
+
+Feature enhancements:
+
+* [FEATURE #2684](https://github.com/BurntSushi/ripgrep/issues/2684):
+  Improve completions for the `fish` shell.
+
+
 14.0.3 (2023-11-28)
 ===================
 This is a patch release with a bug fix for the `--sortr` flag.