Auto-put PRs from release workflows in the proper milestone + minor things (#4862)

* Make workflow name use TitleCase

* Indicate in the PR description that it's a multi-part workflow

* Auto-put PRs from Prepare Release workflow in the proper milestone

* Rename "Publish the release" workflow to "Publish Release"

* Auto-put PR from Publish Release workflow in the proper milestone

.github/workflows/scripts/bump_version.py

@@ -12,6 +12,8 @@ version_info = None
 def repl(match: Match[str]) -> str:
     global version_info
 
+    print(f"::set-output name=old_version::{match.group('version')}")
+
     new_stable_version = os.environ.get("NEW_STABLE_VERSION", "auto")
     if new_stable_version == "auto":
         version_info = redbot.VersionInfo.from_str(match.group("version"))

.github/workflows/scripts/get_milestone_number_by_exact_title.js

@@ -0,0 +1,49 @@
+module.exports = (async function ({github, context}) {
+    const milestone_title = process.env.MILESTONE_TITLE;
+    const [repo_owner, repo_name] = process.env.GITHUB_REPOSITORY.split('/');
+
+    const {
+        repository: {
+            milestones: {
+                nodes: milestones,
+                pageInfo: {hasNextPage}
+            }
+        }
+    } = await github.graphql({
+        query: `
+        query getMilestoneNumberByTitle(
+          $repo_owner: String!
+          $repo_name: String!
+          $milestone_title: String!
+        ) { 
+          repository(owner:$repo_owner name:$repo_name) {
+            milestones(query:$milestone_title states:OPEN first:100) {
+              nodes {
+                number
+                title
+              }
+              pageInfo {
+                hasNextPage
+              }
+            }
+          }
+        }`,
+        repo_owner: repo_owner,
+        repo_name: repo_name,
+        milestone_title: milestone_title,
+    });
+
+    if (hasNextPage) {
+        // this should realistically never happen so let's just error
+        core.setFailed('Impossible happened! :)');
+        return;
+    }
+
+    for (const milestone of milestones)
+        if (milestone.title === milestone_title)
+            return milestone.number;
+
+    // if no exact match is found, assume the milestone doesn't exist
+    console.log('The milestone was not found. API returned the array: %o', milestones);
+    return null;
+})