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

test/functional/test_framework/blocktools.py

@@ -63,6 +63,8 @@ COINBASE_MATURITY = 100
 # From BIP141
 WITNESS_COMMITMENT_HEADER = b"\xaa\x21\xa9\xed"
 
+NULL_OUTPOINT = COutPoint(0, 0xffffffff)
+
 NORMAL_GBT_REQUEST_PARAMS = {"rules": ["segwit"]}
 VERSIONBITS_LAST_OLD_BLOCK_VERSION = 4
 MIN_BLOCKS_TO_KEEP = 288
@@ -177,7 +179,7 @@ def create_coinbase(height, pubkey=None, *, script_pubkey=None, extra_output_scr
     script. This is useful to pad block weight/sigops as needed. """
     coinbase = CTransaction()
     coinbase.nLockTime = height - 1
-    coinbase.vin.append(CTxIn(COutPoint(0, 0xffffffff), script_BIP34_coinbase_height(height), MAX_SEQUENCE_NONFINAL))
+    coinbase.vin.append(CTxIn(NULL_OUTPOINT, script_BIP34_coinbase_height(height), MAX_SEQUENCE_NONFINAL))
     coinbaseoutput = CTxOut()
     coinbaseoutput.nValue = nValue * COIN
     if nValue == 50: