Resolve #3120298 "Test current behavior" - more coverage

Closes #3120298

added 5 commits

• 3fec1ac9 - Test non-implemented and repeated alter types.
• 02836d0f - Test duplicate alter hook listeners.
• 7f11bfc9 - Add FormAlterTest kernel test.
• 6325a206 - Test effect of non-unique alter types on ordering rules.
• 3531692c - Remove leftover part of a doc comment on assertAlterCallOrder().

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