Merge bitcoin/bitcoin#22674: validation: mempool validation and submission for packages of 1 child + parents

046e8ff264 [unit test] package submission (glozow)
e12fafda2d [validation] de-duplicate package transactions already in mempool (glozow)
8310d942e0 [packages] add sanity checks for package vs mempool limits (glozow)
be3ff151a1 [validation] full package accept + mempool submission (glozow)
144a29099a [policy] require submitted packages to be child-with-unconfirmed-parents (glozow)
d59ddc5c3d [packages/doc] define and document package rules (glozow)
ba26169f60 [unit test] context-free package checks (glozow)
9b2fdca7f0 [packages] add static IsChildWithParents function (glozow)

Pull request description:

  This is 1 chunk of [Package Mempool Accept](https://gist.github.com/glozow/dc4e9d5c5b14ade7cdfac40f43adb18a); it restricts packages to 1 child with its parents, doesn't allow conflicts, and doesn't have CPFP (yet).  Future PRs (see #22290) will add RBF and CPFP within packages.

ACKs for top commit:
  laanwj:
    Code review ACK 046e8ff264

Tree-SHA512: 37dbba37d527712f8efef71ee05c90a8308992615af35f5e0cfeafc60d859cc792737d125aac526e37742fe7683ac8c155ac24af562426213904333c01260c95

src/rpc/rawtransaction.cpp

@@ -1028,6 +1028,8 @@ static RPCHelpMan testmempoolaccept()
             continue;
         }
         const auto& tx_result = it->second;
+        // Package testmempoolaccept doesn't allow transactions to already be in the mempool.
+        CHECK_NONFATAL(tx_result.m_result_type != MempoolAcceptResult::ResultType::MEMPOOL_ENTRY);
         if (tx_result.m_result_type == MempoolAcceptResult::ResultType::VALID) {
             const CAmount fee = tx_result.m_base_fees.value();
             // Check that fee does not exceed maximum fee