Fix bug in Merge When Checks Pass needing a pipeline

What does this MR do and why?

Merge When Checks Pass should function when a pipeline does not exist, and is not needed. Currently we inherit from MergeWhenPipelineSucceeds which requires a pipeline.

To test:

• Have a project which does not use pipelines and the setting 'pipeline required to pass' is not checked
• Ensure merge_when_checks_pass and additional_merge_when_checks_ready feature flags are on
• Be on master
• Create an MR that is mergeable except for an approval
• Click Auto Merge
• Click Approve
• It will fail to merge
• Switch to this branch
• Unapprove
• Cancel auto merge
• Click Auto merge
• Approve again
• It should merge fine

Related to: #441316 (closed)

assigned to @marc_shaw

added 1 commit

• ecb162df - Merge when checks pass should not need a pipeline to merge

Compare with previous version

Ahoy hoy @patrickbajao

Mind taking the first review here?

requested review from @patrickbajao

added backend typebug labels

	1 Warning
	This MR changes code in ee/, but its Changelog commit is missing the EE: true trailer. Consider adding it to your Changelog commits.

Reviewer roulette

Category	Reviewer	Maintainer
backend	@mc_rocha (UTC-5, 14 hours behind author)	@j.seto (UTC+0, 9 hours behind author)
test for spec/features/*	@mc_rocha (UTC-5, 14 hours behind author)	Maintainer review is optional for test for spec/features/*

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removed review request for @patrickbajao

E2E Test Result Summary

allure-report-publisher generated test report!

e2e-test-on-gdk: test report for 5a9f0ac8

expand test summary

+------------------------------------------------------------------+
|                          suites summary                          |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| Plan        | 4      | 0      | 0       | 0     | 4     | ✅     |
| Create      | 60     | 0      | 9       | 0     | 69    | ✅     |
| Govern      | 3      | 0      | 0       | 0     | 3     | ✅     |
| Monitor     | 4      | 0      | 0       | 0     | 4     | ✅     |
| Package     | 0      | 0      | 1       | 0     | 1     | ➖     |
| Data Stores | 2      | 0      | 0       | 0     | 2     | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 73     | 0      | 10      | 0     | 83    | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+

e2e-package-and-test: test report for 5a9f0ac8

expand test summary

+------------------------------------------------------------------+
|                          suites summary                          |
+-------------+--------+--------+---------+-------+-------+--------+
|             | passed | failed | skipped | flaky | total | result |
+-------------+--------+--------+---------+-------+-------+--------+
| Create      | 568    | 0      | 58      | 0     | 626   | ✅     |
| Data Stores | 4      | 0      | 0       | 0     | 4     | ✅     |
| Monitor     | 8      | 0      | 0       | 0     | 8     | ✅     |
| Package     | 0      | 0      | 2       | 0     | 2     | ➖     |
| Plan        | 8      | 0      | 0       | 0     | 8     | ✅     |
| Govern      | 6      | 0      | 0       | 0     | 6     | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+
| Total       | 594    | 0      | 60      | 0     | 654   | ✅     |
+-------------+--------+--------+---------+-------+-------+--------+

added groupcode review label

added devopscreate sectiondev labels

requested review from @patrickbajao

changed milestone to %16.10

removed review request for @patrickbajao

closed

reopened

added 728 commits

• ecb162df...367a544a - 727 commits from branch master
• f3c48de3 - Merge when checks pass should not need a pipeline to merge

Compare with previous version

mentioned in issue #442010 (closed)

added 1 commit

• 768c0700 - Merge when checks pass should not need a pipeline to merge

Compare with previous version