Merge bitcoin/bitcoin#26567: Wallet: estimate the size of signed inputs using descriptors

10546a569c wallet: accurately account for the size of the witness stack (Antoine Poinsot)
9b7ec393b8 wallet: use descriptor satisfaction size to estimate inputs size (Antoine Poinsot)
8d870a9873 script/signingprovider: introduce a MultiSigningProvider (Antoine Poinsot)
fa7c46b503 descriptor: introduce a method to get the satisfaction size (Antoine Poinsot)
bdba7667d2 miniscript: introduce a helper to get the maximum witness size (Antoine Poinsot)
4ab382c2cd miniscript: make GetStackSize independent of P2WSH context (Antoine Poinsot)

Pull request description:

  The wallet currently estimates the size of a signed input by doing a dry run of the signing logic. This is unnecessary since all outputs we can sign for can be represented by a descriptor, and we can derive the size of a satisfaction ("signature") directly from the descriptor itself.
  In addition, the current approach does not generalize well: dry runs of the signing logic are only possible for the most basic scripts. See for instance the discussion in #24149 around that.

  This introduces a method to get the maximum size of a satisfaction from a descriptor, and makes the wallet use that instead of the dry-run.

ACKs for top commit:
  sipa:
    utACK 10546a569c
  achow101:
    re-ACK 10546a569c

Tree-SHA512: 43ed1529fbd30af709d903c8c5063235e8c6a03b500bc8f144273d6184e23a53edf0fea9ef898ed57d8a40d73208b5d935cc73b94a24fad3ad3c63b3b2027174

src/wallet/test/spend_tests.cpp

@@ -62,57 +62,6 @@ BOOST_FIXTURE_TEST_CASE(SubtractFee, TestChain100Setup)
     BOOST_CHECK_EQUAL(fee, check_tx(fee + 123));
 }
 
-static void TestFillInputToWeight(int64_t additional_weight, std::vector<int64_t> expected_stack_sizes)
-{
-    static const int64_t EMPTY_INPUT_WEIGHT = GetTransactionInputWeight(CTxIn());
-
-    CTxIn input;
-    int64_t target_weight = EMPTY_INPUT_WEIGHT + additional_weight;
-    BOOST_CHECK(FillInputToWeight(input, target_weight));
-    BOOST_CHECK_EQUAL(GetTransactionInputWeight(input), target_weight);
-    BOOST_CHECK_EQUAL(input.scriptWitness.stack.size(), expected_stack_sizes.size());
-    for (unsigned int i = 0; i < expected_stack_sizes.size(); ++i) {
-        BOOST_CHECK_EQUAL(input.scriptWitness.stack[i].size(), expected_stack_sizes[i]);
-    }
-}
-
-BOOST_FIXTURE_TEST_CASE(FillInputToWeightTest, BasicTestingSetup)
-{
-    {
-        // Less than or equal minimum of 165 should not add any witness data
-        CTxIn input;
-        BOOST_CHECK(!FillInputToWeight(input, -1));
-        BOOST_CHECK_EQUAL(GetTransactionInputWeight(input), 165);
-        BOOST_CHECK_EQUAL(input.scriptWitness.stack.size(), 0);
-        BOOST_CHECK(!FillInputToWeight(input, 0));
-        BOOST_CHECK_EQUAL(GetTransactionInputWeight(input), 165);
-        BOOST_CHECK_EQUAL(input.scriptWitness.stack.size(), 0);
-        BOOST_CHECK(!FillInputToWeight(input, 164));
-        BOOST_CHECK_EQUAL(GetTransactionInputWeight(input), 165);
-        BOOST_CHECK_EQUAL(input.scriptWitness.stack.size(), 0);
-        BOOST_CHECK(FillInputToWeight(input, 165));
-        BOOST_CHECK_EQUAL(GetTransactionInputWeight(input), 165);
-        BOOST_CHECK_EQUAL(input.scriptWitness.stack.size(), 0);
-    }
-
-    // Make sure we can add at least one weight
-    TestFillInputToWeight(1, {0});
-
-    // 1 byte compact size uint boundary
-    TestFillInputToWeight(252, {251});
-    TestFillInputToWeight(253, {83, 168});
-    TestFillInputToWeight(262, {86, 174});
-    TestFillInputToWeight(263, {260});
-
-    // 3 byte compact size uint boundary
-    TestFillInputToWeight(65535, {65532});
-    TestFillInputToWeight(65536, {21842, 43688});
-    TestFillInputToWeight(65545, {21845, 43694});
-    TestFillInputToWeight(65546, {65541});
-
-    // Note: We don't test the next boundary because of memory allocation constraints.
-}
-
 BOOST_FIXTURE_TEST_CASE(wallet_duplicated_preset_inputs_test, TestChain100Setup)
 {
     // Verify that the wallet's Coin Selection process does not include pre-selected inputs twice in a transaction.

src/wallet/test/walletload_tests.cpp

@@ -31,6 +31,9 @@ public:
     bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache = nullptr) const override { return false; };
     bool ExpandFromCache(int pos, const DescriptorCache& read_cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const override { return false; }
     void ExpandPrivate(int pos, const SigningProvider& provider, FlatSigningProvider& out) const override {}
+    std::optional<int64_t> ScriptSize() const override { return {}; }
+    std::optional<int64_t> MaxSatisfactionWeight(bool) const override { return {}; }
+    std::optional<int64_t> MaxSatisfactionElems() const override { return {}; }
 };
 
 BOOST_FIXTURE_TEST_CASE(wallet_load_descriptors, TestingSetup)