refactor(interpreter): extract glob/pattern matching to glob.rs (#748)

## Summary
- Extract ~730 lines of glob pattern matching and expansion code from
the 12K-line `interpreter/mod.rs` into a dedicated `interpreter/glob.rs`
submodule
- Moves pattern matching (extglob, bracket expressions), glob option
helpers, and filesystem glob expansion to the new module
- First step in splitting the god module (Closes #727)

## Test plan
- [x] `cargo check` passes
- [x] `cargo fmt --check` passes
- [x] `cargo clippy --all-targets --all-features -- -D warnings` passes
- [x] `cargo test --all-features` passes (95 passed, 45 ignored)
- [x] All existing glob/pattern tests continue to pass

Author: chaliy