fix(ci): Avoid unnecessary runner allocation by splitting platform matrix into separate jobs #12673

Job	Run time
Ready-to-merge gate / Missing "ready-to-merge" label	3s
Build legacy macos ${{ matrix.build-type }}	0s
detect-changes	0s
Build ${{ matrix.rn-architecture }} ios ${{ matrix.build-type }} ${{ matrix.ios-use-frameworks }}	0s
diff_check	0s
Build ${{ matrix.rn-architecture }} android ${{ matrix.build-type }}	0s
Test ios production REV2	-1s
Test android production REV2	-1s
	1s

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