feature: Add new crate `gix-macros` #3263

Job	Run time
lint	5m 23s
pure-rust-build	4m 13s
cargo-deny (advisories)	36s
cargo-deny (bans licenses sources)	32s
installation (win-msvc)	13m 21s
installation (win-gnu)	11m 36s
installation (win32-msvc)	10m 39s
installation (win32-gnu)	12m 35s
test-32bit	51s
test	37m 20s
test-fast (windows-latest)	9m 57s
test-fast (macos-latest)	9m 1s
test-fast (ubuntu-latest)	6m 19s
WebAssembly (wasm32-unknown-unknown)	1m 46s
WebAssembly (wasm32-wasi)	58s
	2h 5m 7s

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