Bump React Ace to v12

[RichDom2185]

Description

Supersedes #2880.

Also did a bit of cleanup.

Our custom syntax highlighting is still broken at the moment but other syntax highlighting works.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Code quality improvements

How to test

Checklist

• I have tested this code
• I have updated the documentation

[coveralls]

Pull Request Test Coverage Report for Build 8973439585

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 5 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.03%) to 32.078%

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Files with Coverage Reduction	New Missed Lines	%
src/commons/utils/AceHelper.ts	1	31.43%
src/commons/editor/Editor.tsx	4	38.41%

Totals
Change from base Build 8971907944:	-0.03%
Covered Lines:	5006
Relevant Lines:	14652

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💛 - Coveralls