Bip54: add sequence, timestamp (and version) to GBT

Melvin Carvalho recently made a notable update to a proposal, choosing to eliminate the "version" field from both the proposal and its reference implementation. This decision was influenced by an initial aim to ensure that the getblocktemplate function would fully detail the coinbase fields required by a mining pool. However, this objective has been deferred for consideration within a new Bitcoin Improvement Proposal (BIP). The reasoning behind postponing this goal stems from the recognition that BIP145 does not address certain aspects such as the fields for the coinbase witness and the SegWit commitment. Incorporating these elements into the proposal would significantly broaden its scope beyond the original intentions. For further details, one can refer to the discussion and changes made in the pull request at GitHub.