ci: re-enable merge_group and skip jobs for merge queue

GitHub Actions does not allow required status checks to differ between
pull requests and merge queue runs. To work around this, the pull
request workflow must run for merge_group events, but certain jobs—
specifically those marked as required—need to be skipped to avoid
conflicts or redundant execution.

Signed-off-by: Rina Fujino <rina.fujino.23@gmail.com>

Author: rina23q

.github/workflows/pull-request-checks.yml

@@ -3,7 +3,7 @@ name: Pull Request Checks
 on:
   workflow_dispatch:
   pull_request:
-
+  merge_group:
 env:
   CARGO_TERM_COLOR: always
 
@@ -24,6 +24,7 @@ jobs:
   changes:
     name: Filter changes
     runs-on: ubuntu-22.04
+    if: ${{ github.event_name != 'merge_group' }}
     # Set job outputs to values from filter step
     outputs:
       rust: ${{ steps.filter.outputs.rust || 'true' }}
@@ -42,6 +43,7 @@ jobs:
               - 'crates/**'
               - 'plugins/**'
               - 'Cargo.*'
+              - '**/Cargo.toml'
             workflows:
               - '.github/workflows/**'
             docs:
@@ -53,9 +55,8 @@ jobs:
   check-lockfile-uptodate:
     name: Check whether Cargo.lock is up to date
     runs-on: ubuntu-22.04
-    if: ${{ github.event_name == 'pull_request' }}
-    outputs:
-      locks: ${{ steps.filter.outputs.locks }}
+    needs: changes
+    if: ${{ needs.changes.outputs.rust == 'true' || needs.changes.outputs.workflows == 'true' }}
     steps:
       - uses: actions/checkout@v4
 
@@ -74,15 +75,7 @@ jobs:
 
       - uses: Swatinem/rust-cache@v2
 
-      - uses: dorny/paths-filter@v3
-        id: filter
-        with:
-          filters: |
-            locks:
-              - '**/Cargo.toml'
-
       - name: Check whether lockfile is up to date
-        if: steps.filter.outputs.locks == 'true'
         run: cargo check --locked
 
   udeps: