Add Musig2 module #1570

Job	Run time
Test - 1.63.0 toolchain (minimal)	5m 49s
Test - 1.63.0 toolchain (recent)	6m 6s
Test 32-bit version	23s
Docs - stable toolchain (recent)	13s
Format - nightly toolchain	10s
Prepare	3s
WASM - stable toolchain	1m 38s
Test - stable toolchain (minimal)	3m 32s
Test - stable toolchain (recent)	3m 38s
Docs - nightly toolchain (recent)	20s
Test - nightly toolchain (minimal)	2m 50s
Test - nightly toolchain (recent)	2m 49s
Lint - nightly toolchain (recent)	19s
no-std - nightly toolchain (recent)	53s
Bench - nightly toolchain (recent)	20s
ASAN - nightly toolchain (recent)	1m 29s
	30m 32s

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