sagemathgh-35062: Enable merge_group trigger for merge queues

    
### 📚 Description

Two days ago [github announced the public beta of merge
queues](https://github.blog/changelog/2023-02-08-pull-request-merge-
queue-public-beta/). The idea is pretty similar the current
release/merge process (as far as I understand it): Given you want to
merge three PRs into `develop`, you add them to the merge queue and
github will create three temporary branches:
- PR1
- PR1 + PR2 merged
- PR1 + PR2 + PR3 merged

It then runs all checks with the `merge_group` trigger on each branch.
Once all checks for all these temporary branches are successful, the
whole group is merged into `develop`. If there are merge conflicts, say
between PR3 and PR1, or the build for the PR1+2+3 branch fails, then PR3
is removed from the merge queue and only the first two PRs are merged
into `develop`.

In this way, one could never end up in a situation where the checks are
not passing in the develop branch, without requiring devs to always
merge the latest develop branch themselves. (E.g., we will no longer hit
the situation that PR2 introduces new linter rules which are not
fullfiled by PR3 but both PRs are merged into develop).

References:
- https://docs.github.com/en/repositories/configuring-branches-and-
merges-in-your-repository/configuring-pull-request-merges/managing-a-
merge-queue
- https://docs.github.com/en/actions/using-workflows/events-that-
trigger-workflows#merge_group

---

In this PR we add the merge_group trigger on the current PR-workflows,
which enables to run these in the merge queue as well.

---

Since this effectively implements the current version of "Volker's
temporary private develop branch", I was wondering if this would be
eneough to give more people rights to merge PRs. What else would be
necessary for such a step? @vbraun

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### 📝 Checklist

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### ⌛ Dependencies
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URL: sagemath#35062
Reported by: Tobias Diez
Reviewer(s): Dima Pasechnik, Matthias Köppe, Tobias Diez

.github/workflows/build.yml

@@ -2,8 +2,11 @@ name: Build & Test
 
 on:
   pull_request:
+  merge_group:
   push:
-    branches: ['**']
+    branches:
+      - master
+      - develop
     # Ignore pushes on tags to prevent two uploads of codecov reports
     tags-ignore: ['**']
   workflow_dispatch:

.github/workflows/doc-build.yml

@@ -2,7 +2,11 @@ name: Build documentation
 
 on:
   pull_request:
+  merge_group:
   push:
+    branches:
+      - master
+      - develop
   workflow_dispatch:
     # Allow to run manually
 

.github/workflows/lint.yml

@@ -1,6 +1,12 @@
 name: Lint
 
-on: [push, pull_request]
+on: 
+  push:
+    branches:
+      - master
+      - develop
+  pull_request: 
+  merge_group:
 
 concurrency:
   # Cancel previous runs of this workflow for the same branch