Merge bitcoin/bitcoin#24836: add RPC (-regtest only) for testing package policy

e866f0d066 [functional test] submitrawpackage RPC (glozow)
fa076515b0 [rpc] add new submitpackage RPC (glozow)

Pull request description:

  It would be nice for LN/wallet/app devs to test out package policy, package RBF, etc., but the only interface to do so right now is through unit tests. This PR adds a `-regtest` only RPC interface so people can test by submitting raw transaction data. It is regtest-only, as it would be unsafe/confusing to create an actual mainnet interface while package relay doesn't exist.

  Note that the functional tests are there to ensure the RPC interface is working properly; they aren't for testing policy itself. See src/test/txpackage_tests.cpp.

ACKs for top commit:
  t-bast:
    Tested ACK against eclair e866f0d066
  ariard:
    Code Review ACK e866f0d0
  instagibbs:
    code review ACK e866f0d066

Tree-SHA512: 824a26b10d2240e0fd85e5dd25bf499ee3dd9ba8ef4f522533998fcf767ddded9f001f7a005fe3ab07ec95e696448484e26599803e6034ed2733125c8c376c84

test/functional/test_runner.py

@@ -130,6 +130,7 @@ BASE_SCRIPTS = [
     'wallet_address_types.py --descriptors',
     'feature_bip68_sequence.py',
     'p2p_feefilter.py',
+    'rpc_packages.py',
     'feature_reindex.py',
     'feature_abortnode.py',
     # vv Tests less than 30s vv
@@ -231,7 +232,6 @@ BASE_SCRIPTS = [
     'mempool_packages.py',
     'mempool_package_onemore.py',
     'rpc_createmultisig.py',
-    'rpc_packages.py',
     'mempool_package_limits.py',
     'feature_versionbits_warning.py',
     'rpc_preciousblock.py',