Add support for musig() key expressions #1253

Job	Run time
Compilation for NanoS, X, S+, and Stax (nanos, $NANOS_SDK)	1m 43s
Compilation for NanoS, X, S+, and Stax (nanox, $NANOX_SDK)	1m 49s
Compilation for NanoS, X, S+, and Stax (nanosp, $NANOSP_SDK)	2m 4s
Compilation for NanoS, X, S+, and Stax (stax, $STAX_SDK)	1m 57s
Tests with the Python library and legacy Bitcoin app	42s
Tests on mainnet (nanos)	29s
Tests on mainnet (nanox)	29s
Tests with the JS library	1m 40s
Tests on mainnet (nanosp)	33s
Tests for rust client library	1m 44s
Tests on mainnet (stax)	29s
Unit test	1m 50s
	15m 29s

Provide feedback