ecdsa_adaptor: add nonce function and tags

This commit adds a nonce function that will be used by default
for ECDSA adaptor signatures.

This nonce function is similar to secp256k1_nonce_function_hardened
except it uses the compressed 33-byte encoding for the pubkey argument.
We need 33 bytes instead of 32 because, unlike with BIP-340, an ECDSA
X-coordinate alone is not sufficient to disambiguate the Y-coordinate.

src/modules/ecdsa_adaptor/Makefile.am.include

@@ -1 +1,2 @@
 include_HEADERS += include/secp256k1_ecdsa_adaptor.h
+noinst_HEADERS += src/modules/ecdsa_adaptor/main_impl.h