Add Musig2 module #1568

Job	Run time
Docs - stable toolchain (recent)	18s
Format - nightly toolchain	14s
Test 32-bit version	24s
Test - 1.63.0 toolchain (minimal)	5m 54s
Prepare	2s
Test - stable toolchain (minimal)	3m 40s
Test - 1.63.0 toolchain (recent)	5m 57s
Test - stable toolchain (recent)	3m 31s
WASM - stable toolchain	1m 33s
Test - nightly toolchain (minimal)	2m 49s
Test - nightly toolchain (recent)	2m 43s
Docs - nightly toolchain (recent)	19s
Bench - nightly toolchain (recent)	22s
ASAN - nightly toolchain (recent)	1m 28s
Lint - nightly toolchain (recent)	22s
no-std - nightly toolchain (recent)	43s
	30m 19s

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