Extract ClearCodec from `ironrdp-graphics` into `ironrdp-clearcodec`

Following the pattern established in parent issue, ClearCodec is the next codec to extract: largely self-contained inside `ironrdp-graphics` (`clearcodec/{mod,glyph_cache,vbar_cache}.rs`), with a clear consumer (EGFX WireToSurface dispatch).

## Goal

Validate the per-codec-crate template against a non-trivial real codec, and reduce `ironrdp-graphics` scope by one codec.

## Scope

- Move `crates/ironrdp-graphics/src/clearcodec/` → `crates/ironrdp-clearcodec/`.
- Promote any `pub(crate)` primitives ClearCodec relies on to `pub` in `ironrdp-graphics`. Document them.
- Update `ironrdp-egfx` and other consumers.
- Re-export from `ironrdp-graphics` with `#[deprecated]` for one release cycle.

## Notes

- ClearCodec depends on `ironrdp_pdu::codecs::clearcodec` for stream parsing. Acceptable interim cost; cleaner dependency falls under #1352.