Add `tool dir` and `toolchain dir` commands (#4695)
## Summary
Resolves #4483
Resolves #4484
## Test Plan
`cargo test`
```sh
❯ cargo run -- toolchain dir
warning: `uv toolchain dir` is experimental and may change without warning.
/Users/ahmedilyas/Library/Application Support/uv/toolchains
❯ cargo run -- tool dir
warning: `uv tool dir` is experimental and may change without warning.
/Users/ahmedilyas/Library/Application Support/uv/tools
```
