miner: Make mempool optional for BlockAssembler

...also adjust callers

Changes:

- In BlockAssembler::CreateNewBlock, we now only lock m_mempool->cs and
  call addPackageTxs if m_mempool is not nullptr
- BlockAssembler::addPackageTxs now takes in a mempool reference, and is
  annotated to require that mempool's lock.
- In TestChain100Setup::CreateBlock and generateblock, don't construct
  an empty mempool, just pass in a nullptr for mempool

src/test/blockfilter_index_tests.cpp

@@ -65,7 +65,7 @@ CBlock BuildChainTestingSetup::CreateBlock(const CBlockIndex* prev,
     const std::vector<CMutableTransaction>& txns,
     const CScript& scriptPubKey)
 {
-    std::unique_ptr<CBlockTemplate> pblocktemplate = BlockAssembler{m_node.chainman->ActiveChainstate(), *m_node.mempool}.CreateNewBlock(scriptPubKey);
+    std::unique_ptr<CBlockTemplate> pblocktemplate = BlockAssembler{m_node.chainman->ActiveChainstate(), m_node.mempool.get()}.CreateNewBlock(scriptPubKey);
     CBlock& block = pblocktemplate->block;
     block.hashPrevBlock = prev->GetBlockHash();
     block.nTime = prev->nTime + 1;

src/test/fuzz/tx_pool.cpp

@@ -97,7 +97,7 @@ void Finish(FuzzedDataProvider& fuzzed_data_provider, MockedTxPool& tx_pool, CCh
         BlockAssembler::Options options;
         options.nBlockMaxWeight = fuzzed_data_provider.ConsumeIntegralInRange(0U, MAX_BLOCK_WEIGHT);
         options.blockMinFeeRate = CFeeRate{ConsumeMoney(fuzzed_data_provider, /*max=*/COIN)};
-        auto assembler = BlockAssembler{chainstate, *static_cast<CTxMemPool*>(&tx_pool), options};
+        auto assembler = BlockAssembler{chainstate, &tx_pool, options};
         auto block_template = assembler.CreateNewBlock(CScript{} << OP_TRUE);
         Assert(block_template->block.vtx.size() >= 1);
     }

src/test/miner_tests.cpp

@@ -52,7 +52,7 @@ BlockAssembler MinerTestingSetup::AssemblerForTest(const CChainParams& params)
 
     options.nBlockMaxWeight = MAX_BLOCK_WEIGHT;
     options.blockMinFeeRate = blockMinFeeRate;
-    return BlockAssembler{m_node.chainman->ActiveChainstate(), *m_node.mempool, options};
+    return BlockAssembler{m_node.chainman->ActiveChainstate(), m_node.mempool.get(), options};
 }
 
 constexpr static struct {

src/test/util/mining.cpp

@@ -77,7 +77,7 @@ CTxIn MineBlock(const NodeContext& node, const CScript& coinbase_scriptPubKey)
 std::shared_ptr<CBlock> PrepareBlock(const NodeContext& node, const CScript& coinbase_scriptPubKey)
 {
     auto block = std::make_shared<CBlock>(
-        BlockAssembler{Assert(node.chainman)->ActiveChainstate(), *Assert(node.mempool)}
+        BlockAssembler{Assert(node.chainman)->ActiveChainstate(), Assert(node.mempool.get())}
             .CreateNewBlock(coinbase_scriptPubKey)
             ->block);
 

src/test/util/setup_common.cpp

@@ -277,8 +277,7 @@ CBlock TestChain100Setup::CreateBlock(
     const CScript& scriptPubKey,
     CChainState& chainstate)
 {
-    CTxMemPool empty_pool;
-    CBlock block = BlockAssembler{chainstate, empty_pool}.CreateNewBlock(scriptPubKey)->block;
+    CBlock block = BlockAssembler{chainstate, nullptr}.CreateNewBlock(scriptPubKey)->block;
 
     Assert(block.vtx.size() == 1);
     for (const CMutableTransaction& tx : txns) {

src/test/validation_block_tests.cpp

@@ -65,7 +65,7 @@ std::shared_ptr<CBlock> MinerTestingSetup::Block(const uint256& prev_hash)
     static int i = 0;
     static uint64_t time = Params().GenesisBlock().nTime;
 
-    auto ptemplate = BlockAssembler{m_node.chainman->ActiveChainstate(), *m_node.mempool}.CreateNewBlock(CScript{} << i++ << OP_TRUE);
+    auto ptemplate = BlockAssembler{m_node.chainman->ActiveChainstate(), m_node.mempool.get()}.CreateNewBlock(CScript{} << i++ << OP_TRUE);
     auto pblock = std::make_shared<CBlock>(ptemplate->block);
     pblock->hashPrevBlock = prev_hash;
     pblock->nTime = ++time;
@@ -327,7 +327,7 @@ BOOST_AUTO_TEST_CASE(witness_commitment_index)
 {
     CScript pubKey;
     pubKey << 1 << OP_TRUE;
-    auto ptemplate = BlockAssembler{m_node.chainman->ActiveChainstate(), *m_node.mempool}.CreateNewBlock(pubKey);
+    auto ptemplate = BlockAssembler{m_node.chainman->ActiveChainstate(), m_node.mempool.get()}.CreateNewBlock(pubKey);
     CBlock pblock = ptemplate->block;
 
     CTxOut witness;