chore: update GitHub Actions CI + remove redundant job (#19)

The following updates are performed:
* update [`actions/checkout`](https://github.com/actions/checkout) to v3
* replace
[unmaintained](actions-rs/toolchain#216)
`actions-rs/toolchain` by
[`dtolnay/rust-toolchain`](https://github.com/dtolnay/rust-toolchain)
* replace unmaintained `actions-rs/cargo` by direct invocations of
`cargo`

Still using the outdated / unmaintained actions will generate several
warnings in CI runs, for example in
https://github.com/alexkirsz/dispatch/actions/runs/4903327790:

> Node.js 12 actions are deprecated. Please update the following actions
to use Node.js 16: actions/checkout@v2, actions-rs/toolchain@v1,
actions-rs/cargo@v1. For more information see:
https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/.

The PR will get rid of those warnings.


Futhermore, the redundant `combo` job is removed, because just does what
the the two previous jobs ('Clippy` and `Format`) in the same workflow
do, so there's no need to keep it.

.github/workflows/nightly_lints.yml

@@ -1,5 +1,3 @@
-# Based on https://github.com/actions-rs/meta
-
 on: [push, pull_request]
 
 name: Nightly lints
@@ -13,19 +11,13 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Install nightly toolchain with clippy available
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
-          profile: minimal
           toolchain: nightly
-          override: true
           components: clippy
 
       - name: Run cargo clippy
-        uses: actions-rs/cargo@v1
-        continue-on-error: true  # WARNING: only for this example, remove it!
-        with:
-          command: clippy
-          args: -- -D warnings
+        run: cargo clippy -- -D warnings
 
   rustfmt:
     name: Format
@@ -35,45 +27,10 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Install nightly toolchain with rustfmt available
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
-          profile: minimal
           toolchain: nightly
-          override: true
           components: rustfmt
 
       - name: Run cargo fmt
-        uses: actions-rs/cargo@v1
-        continue-on-error: true  # WARNING: only for this example, remove it!
-        with:
-          command: fmt
-          args: --all -- --check
-
-  combo:
-    name: Clippy + rustfmt
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout sources
-        uses: actions/checkout@v3
-
-      - name: Install nightly toolchain
-        uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: nightly
-          override: true
-          components: rustfmt, clippy
-
-      - name: Run cargo fmt
-        uses: actions-rs/cargo@v1
-        continue-on-error: true  # WARNING: only for this example, remove it!
-        with:
-          command: fmt
-          args: --all -- --check
-
-      - name: Run cargo clippy
-        uses: actions-rs/cargo@v1
-        continue-on-error: true  # WARNING: only for this example, remove it!
-        with:
-          command: clippy
-          args: -- -D warnings
+        run: cargo fmt --all -- --check

.github/workflows/test.yml

@@ -10,62 +10,46 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Install stable toolchain
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
-          profile: minimal
           toolchain: stable
-          override: true
 
       - name: Run cargo check
-        uses: actions-rs/cargo@v1
-        with:
-          command: check
+        run: cargo check
 
   test:
     name: Test Suite
     runs-on: ubuntu-latest
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Install stable toolchain
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
-          profile: minimal
           toolchain: stable
-          override: true
 
       - name: Run cargo test
-        uses: actions-rs/cargo@v1
-        with:
-          command: test
+        run: cargo test
 
   lints:
     name: Lints
     runs-on: ubuntu-latest
     steps:
       - name: Checkout sources
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Install stable toolchain
-        uses: actions-rs/toolchain@v1
+        uses: dtolnay/rust-toolchain@master
         with:
-          profile: minimal
           toolchain: stable
-          override: true
           components: rustfmt, clippy
 
       - name: Run cargo fmt
-        uses: actions-rs/cargo@v1
-        with:
-          command: fmt
-          args: --all -- --check
+        run: cargo fmt --all -- --check
 
       - name: Run cargo clippy
-        uses: actions-rs/cargo@v1
-        with:
-          command: clippy
-          args: -- -D warnings
+        run: cargo clippy -- -D warnings