Merge bitcoin/bitcoin#33819: mining: getCoinbase() returns struct instead of raw tx

48f57bb35b mining: add new getCoinbaseTx() returning a struct (Sjors Provoost)
d59b4cdb57 mining: rename getCoinbaseTx() to ..RawTx() (Sjors Provoost)

Pull request description:

  The first commit renames `getCoinbaseTx()` to `getCoinbaseRawTx()` to reflect that it returns a serialised transaction. This does not impact IPC clients, because they do not use the function name.

  The second commit then introduces a replacement `getCoinbase()` that provides a struct with everything clients need to construct a coinbase. This avoids clients having to parse and manipulate our dummy transaction.

  Deprecate but don't remove `getCoinbaseRawTx()`, `getCoinbaseCommitment()` and `getWitnessCommitmentIndex()`.

  After this change we can drop these deprecated methods, which in turn would allow us to clear the dummy transaction from the `getBlock()` result. But that is left for a followup to keep this PR focussed. See https://github.com/Sjors/bitcoin/pull/106 for an approach.

  Expand the `interface_ipc.py` functional test to document its usage.

  Can be tested using:
  - https://github.com/stratum-mining/sv2-tp/pull/59

ACKs for top commit:
  ryanofsky:
    Code review ACK 48f57bb35b. Just rebased and addressed comments and dropped coinbase tx "template" suffix, which is a nice change
  ismaelsadeeq:
    code review ACK 48f57bb35b
  vasild:
    ACK 48f57bb35b

Tree-SHA512: c4f1d752777fb3086a1a0b7b8b06e4205dbe2f3adb41f218855ad1dee952adccc263cf82acd3bf9300cc83c2c64cebd2b27f66a69beee32d325b9a85e3643b0d

doc/release-notes-33819.md

@@ -0,0 +1,8 @@
+Mining IPC
+----------
+
+- The `getCoinbaseTx()` method is renamed to `getCoinbaseRawTx()` and deprecated.
+  IPC clients do not use the function name, so they're not affected. (#33819)
+- Adds `getCoinbaseTx()` which clients should use instead of `getCoinbaseRawTx()`. It
+  contains all fields required to construct a coinbase transaction, and omits the
+  dummy output which Bitcoin Core uses internally. (#33819)