workflows/pr: rename to pull-request-target

To be able to disable the pr.yml workflow on GitHub, we need to rename
it to a different name. Let's use the long name for consistency with
merge-group.yml. This only affects the GitHub-internal name, not the
visible name in the PR checklist, which is still "PR". This visible name
is also used by nixpkgs-review, so that won't break.

.github/workflows/README.md

@@ -64,7 +64,7 @@ This results in a key with the following semantics:
 
 ## Required Status Checks
 
-The "Required Status Checks" branch ruleset is implemented in two top-level workflows: `pr.yml` and `merge-group.yml`.
+The "Required Status Checks" branch ruleset is implemented in two top-level workflows: `pull-request-target.yml` and `merge-group.yml`.
 
 The PR workflow defines all checks that need to succeed to add a Pull Request to the Merge Queue.
 If no Merge Queue is set up for a branch, the PR workflow defines the checks required to merge into the target branch.

.github/workflows/reviewers.yml

@@ -102,7 +102,7 @@ jobs:
             const run_id = (await github.rest.actions.listWorkflowRuns({
               owner: context.repo.owner,
               repo: context.repo.repo,
-              workflow_id: context.eventName === 'pull_request' ? 'test.yml' : 'pr.yml',
+              workflow_id: context.eventName === 'pull_request' ? 'test.yml' : 'pull-request-target.yml',
               event: context.eventName,
               head_sha: context.payload.pull_request.head.sha
             })).data.workflow_runs[0].id

.github/workflows/test.yml

@@ -63,7 +63,7 @@ jobs:
               '.github/workflows/eval.yml',
               '.github/workflows/labels.yml',
               '.github/workflows/lint.yml',
-              '.github/workflows/pr.yml',
+              '.github/workflows/pull-request-target.yml',
               '.github/workflows/reviewers.yml',
               '.github/workflows/test.yml',
             ].includes(file))) core.setOutput('pr', true)
@@ -87,7 +87,7 @@ jobs:
     if: needs.prepare.outputs.pr
     name: PR
     needs: [prepare]
-    uses: ./.github/workflows/pr.yml
+    uses: ./.github/workflows/pull-request-target.yml
     # Those are actually only used on the pull_request_target event, but will throw an error if not set.
     permissions:
       issues: write