Inner Blocks: Refactor treatment of block settings

[aduth]

This pull request seeks to apply a few refactorings to the InnerBlocks treatment of its nested settings, namely:

• Update deprecated componentWillReceiveProps to equivalent componentDidUpdate (per suggestion at Block List: Remove createInnerBlockList utility / context #7192 (comment))
• Avoid deep equality check on flat allowedBlocks prop shape
• Avoid handling unexpected case where UPDATE_BLOCK_LIST_SETTINGS is not passed an id (was never tested anyways)
• Avoid creating new references for blockListSettings when settings not set, but the id never existed in state anyways (including new test)
• Avoid switch fallthrough on case where previous updateIsRequired condition would be false, which could have introduced future maintainability issues if additional case statements were added
• Update tests to realistic values
• Add test to verify state reference is not changed when no update is needed
• Consistently name allowedBlocks (previously also referred to as supportedBlocks)

Testing instructions:

Repeat testing instructions from #6546.

[aduth]

Seeing that a few of these refactorings were also proposed as part of #6991.

[jorgefilipecosta]

Hi @aduth thank you for this refactoring. I'm sorry I totally lost this PR in the middle of notifications and just noticed it now when new notifications were triggered :(
But the changes here look good 👍