Add `DefinedMacros` handler #7506

Job	Run time
build test linux x86-64	1m 6s
doc tests	3m 20s
build test windows x86-64	5m 7s
check-rust	1m 47s
check-website	17s
scarb-metadata compatibility check	47s
test ${{ matrix.platform.name }} ${{ matrix.partition }}/8	0s
	12m 24s

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