feat: Add custom completer for cargo <TAB> to complete aliases defined in config.toml

[nooma-42]

What does this PR try to resolve?

Related to #14520

This PR introduces auto-completion for the cargo <TAB> option. When a user types cargo <TAB> and presses the TAB key, the system will automatically suggest aliases defined in config.toml

How should we test and review this PR?

To verify this feature, follow these steps:

1. In the terminal, type cargo <TAB>
2. Press the TAB key.
3. You should see aliases suggestions

2025-03-17.4.32.11.mov

[rustbot]

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[nooma-42]

Could you shed some light why would this fail? This seems to me that the compiling output is different? since I'm not working with x86_64 linux, could it be some platform specific error?

failures:

---- basic stdout ----
running `/home/runner/work/cargo/cargo/target/debug/cargo check -Zbuild-std -Zpublic-dependency --target x86_64-unknown-linux-gnu`
running `/home/runner/work/cargo/cargo/target/debug/cargo build -Zbuild-std -Zpublic-dependency --target x86_64-unknown-linux-gnu`
running `/home/runner/work/cargo/cargo/target/debug/cargo run -Zbuild-std -Zpublic-dependency --target x86_64-unknown-linux-gnu`
running `/home/runner/work/cargo/cargo/target/debug/cargo test -Zbuild-std -Zpublic-dependency --target x86_64-unknown-linux-gnu`

thread 'basic' panicked at tests/build-std/main.rs:173:10:

---- expected: tests/build-std/main.rs:161:27
++++ actual:   stderr
   1      - [COMPILING] rustc-std-workspace-std [..]
        1 + [COMPILING] unicode-width v0.1.14
   2    2 | ...
   3    3 | [COMPILING] test v0.0.0 ([..])
   4    4 | [COMPILING] foo v0.0.1 ([ROOT]/foo)
   5    5 | [FINISHED] `test` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
   6    6 | [RUNNING] unittests src/lib.rs (target/[HOST_TARGET]/debug/deps/foo-[HASH])
   7    7 | [RUNNING] unittests src/main.rs (target/[HOST_TARGET]/debug/deps/foo-[HASH])
   8    8 | [RUNNING] tests/smoke.rs (target/[HOST_TARGET]/debug/deps/smoke-[HASH])
error: test failed, to rerun pass `-p cargo --test build-std`
   9    9 | [DOCTEST] foo

Update with SNAPSHOTS=overwrite

note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    basic

test result: FAILED. 6 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in [56](https://github.com/rust-lang/cargo/actions/runs/13917114566/job/38942064437?pr=15319#step:6:57).88s

[weihanglo]

@nooma-42 I'll look into build-std failure today.

[weihanglo]

A rebase onto master should fix the CI failure.

[epage]

Thanks!