[roll] Roll fuchsia [zxsh] Migrate to line-editor

Migrate zxsh from the C linenoise library to the pure-Rust
line-editor crate:
- Replace //zircon/third_party/ulib/linenoise dependency with
  //src/lib/line-editor in BUILD.gn.
- Remove C FFI bindings in src/repl/linenoise.rs.
- Update autocompletion to return Vec<BString> directly to
  line-editor's completion callback.
- Drive interactive REPL sessions using line-editor's Editor,
  supporting command history, interrupt handling, and completion.
- Add comprehensive interactive unit tests for line execution,
  history recording, EOF handling, and completion integration.
- Update documentation in README.md.

Test: fx test zxsh_tests
Original-Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1802261
Original-Original-Revision: ed63d5dc167f31fc65756a96219c56248f03feae
GitOrigin-RevId: b2f975af6709f694cb207c2ae669d735a1e6d644
Change-Id: I0ddf1f8c30d98750c44ff669909b09cc8240c610
Reviewed-on: https://fuchsia-review.googlesource.com/c/integration/+/1803078
Cr-Commit-Position: refs/heads/main@{#201143}