Add Musig2 module #1572

Job	Run time
Test - 1.63.0 toolchain (minimal)	5m 48s
Test - 1.63.0 toolchain (recent)	5m 47s
Test 32-bit version	29s
Docs - stable toolchain (recent)	10s
Prepare	5s
Format - nightly toolchain	11s
WASM - stable toolchain	1m 31s
Test - stable toolchain (minimal)	3m 39s
Test - stable toolchain (recent)	3m 37s
Lint - nightly toolchain (recent)	20s
Bench - nightly toolchain (recent)	20s
Test - nightly toolchain (minimal)	2m 45s
Test - nightly toolchain (recent)	2m 44s
Docs - nightly toolchain (recent)	17s
ASAN - nightly toolchain (recent)	1m 26s
no-std - nightly toolchain (recent)	41s
	29m 50s

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