Supersedes D11762

• As per T2503, this master diff refactors SendXec() to piece together the new suite of utility functions (D11617, D11626, D11645, D11719, D11710, D11712) to send XEC txs via the chronik client.
• This diff aligns to the recent refactor to utxo signing logic in D11854
• The previous post-sending lag issue in D11762 is no longer present due to the recent utxo battery diff.
• handleEncryptedOpReturn() is now redundant and will be deprecated in a separate diff.

• npm test and ensure all existing sendXec unit tests pass
• npm start
• send one to one XEC tx with no message, verify tx details in explorer and in-app
• send one to one XEC tx with message, incl. verify OP_RETURN hex breakdown
• send one to one XEC tx with encrypted message, incl. verify OP_RETURN hex breakdown
• send one to many XEC tx with no message
• send one to many XEC tx with message
• send airdrop with no message and verify OP_RETURN hex breakdown
• send airdrop with message and verify OP_RETURN hex breakdown
• create a new wallet and send a first XEC tx
• activate another saved wallet and send a XEC tx