Add support for musig() key expressions #1329

Job	Run time
Compilation for X, S+, Stax and Flex (nanox, $NANOX_SDK)	1m 39s
Compile the UX-less version of the app on Nano S+ for performance tests	1m 21s
Compilation for X, S+, Stax and Flex (nanosp, $NANOSP_SDK)	1m 49s
Compilation for X, S+, Stax and Flex (stax, $STAX_SDK)	1m 57s
Compilation for X, S+, Stax and Flex (flex, $FLEX_SDK)	1m 52s
Performance report	4m 6s
Tests with the Python library and legacy Bitcoin app	41s
Tests on mainnet (nanox)	29s
Tests with the JS library	1m 14s
Tests on mainnet (nanosp)	29s
Tests for rust client library	1m 36s
Tests on mainnet (stax)	25s
Unit test	2m 6s
Tests on mainnet (flex)	25s
	20m 9s

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