ipc mining: remove deprecated methods (incompatible schema change)

This change removes deprecated methods from the ipc mining interface.

Warning: This is an intermediate, review-only commit. Binaries built from it
should not be distributed or used to connect to other clients or servers. It
makes incompatible changes to the `mining.capnp` schema without updating the
`Init.makeMining` version, causing binaries to advertise support for a schema
they do not actually implement. Mixed versions may therefore exchange garbage
requests/responses instead of producing clear errors. The final commit in this
series bumps the mining interface number to ensure mismatches are detected.

git-bisect-skip: yes

test/functional/test_framework/ipc_util.py

@@ -12,7 +12,7 @@ from pathlib import Path
 import shutil
 from typing import Optional
 
-from test_framework.messages import CBlock, CTransaction
+from test_framework.messages import CBlock
 
 # Test may be skipped and not have capnp installed
 try:
@@ -129,14 +129,6 @@ async def mining_get_block(block_template, ctx):
     return block
 
 
-async def mining_get_coinbase_raw_tx(block_template, ctx):
-    assert block_template is not None
-    coinbase_data = BytesIO((await block_template.getCoinbaseRawTx(ctx)).result)
-    tx = CTransaction()
-    tx.deserialize(coinbase_data)
-    return tx
-
-
 async def mining_get_coinbase_tx(block_template, ctx) -> CoinbaseTxData:
     assert block_template is not None
     # Note: the template_capnp struct will be garbage-collected when this