Merge bitcoin/bitcoin#26415: rpc,rest,zmq: faster getblock, NotifyBlock and rest_block by reading raw block

e710cefd57 rest: read raw block in rest_block and deserialize for json (Andrew Toth)
95ce0783a6 rpc: read raw block in getblock and deserialize for verbosity > 0 (Andrew Toth)
0865ab8712 test: check more details on zmq raw block response (Andrew Toth)
38265cc14e zmq: read raw block with ReadRawBlockFromDisk (Andrew Toth)
da338aada7 blockstorage: check nPos in ReadRawBlockFromDisk before seeking back (Andrew Toth)

Pull request description:

  For the `getblock` endpoint with `verbosity=0`, the  `rest_block` REST endpoint for `bin` and `hex`, and zmq `NotifyBlock` we don't have to deserialize the block since we're just sending the raw data. This PR uses `ReadRawBlockFromDisk` instead of `ReadBlockFromDisk` to serve these requests, and only deserializes for `verbosity > 0` and `json` REST requests. See benchmarks in https://github.com/bitcoin/bitcoin/pull/26684.

  Benchmarked using ApacheBench. Requesting block 750,000 in binary 10k times on a single core (set `-rest=1` in config):
  `ab -n 10000 -c 1 "http://127.0.0.1:8332/rest/block/0000000000000000000592a974b1b9f087cb77628bb4a097d5c2c11b3476a58e.bin"`

  On master, mean time 15ms.
  On this branch, mean time 1ms.

  For RPC
  ```
  echo '{"jsonrpc": "1.0", "id": "curltest", "method": "getblock", "params": ["0000000000000000000592a974b1b9f087cb77628bb4a097d5c2c11b3476a58e", 0]}' > /tmp/data.json
  ab -p /tmp/data.json -n 1000 -c 1 -A user:password "http://127.0.0.1:8332/"
  ```
  On master, mean time 32ms
  On this branch, mean time 13ms

ACKs for top commit:
  achow101:
    re-ACK e710cefd57

Tree-SHA512: 4cea13c7b563b2139d041b1fdcfdb793c8cc688654ae08db07e7ee6b875c5e582b8185db3ae603abbfb06d2164724f29205774620b48c493726b991999af289e

test/functional/interface_zmq.py

@@ -5,6 +5,7 @@
 """Test the ZMQ notification interface."""
 import struct
 from time import sleep
+from io import BytesIO
 
 from test_framework.address import (
     ADDRESS_BCRT1_P2WSH_OP_TRUE,
@@ -17,6 +18,7 @@ from test_framework.blocktools import (
 )
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.messages import (
+    CBlock,
     hash256,
     tx_from_hex,
 )
@@ -201,8 +203,13 @@ class ZMQTest (BitcoinTestFramework):
             assert_equal(tx.hash, txid.hex())
 
             # Should receive the generated raw block.
-            block = rawblock.receive()
-            assert_equal(genhashes[x], hash256_reversed(block[:80]).hex())
+            hex = rawblock.receive()
+            block = CBlock()
+            block.deserialize(BytesIO(hex))
+            assert block.is_valid()
+            assert_equal(block.vtx[0].hash, tx.hash)
+            assert_equal(len(block.vtx), 1)
+            assert_equal(genhashes[x], hash256_reversed(hex[:80]).hex())
 
             # Should receive the generated block hash.
             hash = hashblock.receive().hex()