Add BIP-341 specified constraints to ComputeTaprootMerkleRoot

BIP 341 specifies constraints on the size of the control block _c_ used
to compute the taproot merkle root.

> The last stack element is called the control block _c_, and must have
> length _33 + 32m_, for a value of m that is an integer between 0 and
> 128, inclusive. Fail if it does not have such a length.

(See BIP-341 "Script Validation Rules" here: https://github.com/bitcoin/bips/blob/master/bip-0341.mediawiki#script-validation-rules)

Author: david-bakin

src/script/interpreter.cpp

@@ -1832,6 +1832,10 @@ uint256 ComputeTapleafHash(uint8_t leaf_version, const CScript& script)
 
 uint256 ComputeTaprootMerkleRoot(Span<const unsigned char> control, const uint256& tapleaf_hash)
 {
+    assert(control.size() >= TAPROOT_CONTROL_BASE_SIZE);
+    assert(control.size() <= TAPROOT_CONTROL_MAX_SIZE);
+    assert((control.size() - TAPROOT_CONTROL_BASE_SIZE) % TAPROOT_CONTROL_NODE_SIZE == 0);
+
     const int path_len = (control.size() - TAPROOT_CONTROL_BASE_SIZE) / TAPROOT_CONTROL_NODE_SIZE;
     uint256 k = tapleaf_hash;
     for (int i = 0; i < path_len; ++i) {