docs(help): Fill in styles docs

feat(help): Allow customizing terminal styling (unstable)

For now, this is behind the `unstable-styles` feature as we verify this
is what we want for #3224

Random fixes along the way
- In one case the space after `tip:` was "colored" (won't matter unti...

Because this doesn't have a full section after it, people might want to
style it differently tha...

We can add a new style and default it to what it was split out of
without a breaking change.

chore: Update from '_rust/main' template

This will make reviewing auto-update PRs easier

refactor: Track term widths as plugins

chore: Update anstyle/anstream

chore: Update from '_rust/main' template

fix(typo): replace ags by args

chore(deps): update msrv to v1.65.0

Doing so can cause unnecessary recompilation

fix(error): Don't highlight 'similar'

fix!: Remove `unstable-replace` feature flag

fix(lex): Clarify unsafe safety

fix!: Remove stablized `unstable-grouped` feature

fix(lex): Deprecate unsound `OsStrExt::split_at`

Inspired by #4808

fix(error): Give more idea why we are suggesting an arg

This has been implemented for 3 years without much traction for
finishing it up.

The subcommand...

This is a followup to comments on #4802

fix(error): Change from neutral 'note' to helpful 'tip'

feat(help): Allow user-provided styled text in `StyledStr`

One challenge with this is finding something that generally works.
Making this work perfectly fo...

This also has the advantage of aligning with `error:`

This is a small part of #4638

Fixes #3108
Fixes #1433

We might have respected `NO_COLOR` before via `termcolor`.

See #4722

fix(lex): Allow reporting errors for non-UTF8 longs

feat(derive): Support `#[group]` attributes

perf!(lex): Build faster by removing `os_str_bytes`

refactor: Split out clap_builder for faster derive builds

doc: Clean up cfgs

docs(clap_complete): clap_complete example documentation updated with corresponding file names