Fix clippy warnings and add new workflow clippy (#306)

* Derive `Eq` for `PkgFmt`, `PkgFmtDecomposed` & `TarBasedFmt`
* Derive `Eq` for `PkgMeta`, `PkgOverride` & `BinMeta`
* Rm unnecessary reborrow in `install_from_source`
* Rm unnecessary `into()` in `args::parse`
* Fix `clippy` warning in `CratesToml::append_to_path`
* Fix clippy warning in `cratesio_url`
* Fix clippy warning in `detect_targets_linux`
* Add `clippy` and `rustfmt` to workflow `unit-test`

Because `clippy` would not check inactive code disabled by `cfg`, so we
have to also run `clippy` on multiple targets.

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

.github/workflows/unit-tests.yml

@@ -27,7 +27,7 @@ jobs:
     - uses: actions/checkout@v3
     - name: Configure toolchain
       run: |
-        rustup toolchain install --profile minimal --no-self-update nightly
+        rustup toolchain install nightly --component rustfmt,clippy --no-self-update --profile minimal
         rustup default nightly
 
     - name: Configure caching
@@ -53,3 +53,9 @@ jobs:
     - name: Test (Windows)
       if: matrix.os == 'windows'
       run: cargo test --no-default-features --features native-tls
+
+    - name: fmt
+      run: cargo fmt --all --check
+
+    - name: clippy
+      run: cargo clippy --no-deps -- -D clippy::all