Merge bitcoin/bitcoin#31288: Add destroy to BlockTemplate schema

9aa5015 Add destroy to BlockTemplate schema (Sjors Provoost)

Pull request description:

  This ensures that if a client no longer needs a block template, the node can clear its memory as soon as possible.

  A block template may hold on to transactions that are no longer in the mempool, so this can be significant.

  This has a trivial silent merge conflict with #31283 because it also used the number `@9` (gaps are not allowed). I'll rebase whichever is merged last.

ACKs for top commit:
  TheCharlatan:
    Re-ACK 9aa5015
  ryanofsky:
    Code review ACK 9aa5015

Tree-SHA512: 393571b4455969cba71c7572feaeff4503738205331ab198b9181c156c75eb65933a8e5ceff66fc06d1efb8f2528bdb254e5eee7df75735b912526de1e7b166d

src/ipc/capnp/mining.capnp

@@ -24,15 +24,16 @@ interface Mining $Proxy.wrap("interfaces::Mining") {
 }
 
 interface BlockTemplate $Proxy.wrap("interfaces::BlockTemplate") {
-    getBlockHeader @0 (context: Proxy.Context) -> (result: Data);
-    getBlock @1 (context: Proxy.Context) -> (result: Data);
-    getTxFees @2 (context: Proxy.Context) -> (result: List(Int64));
-    getTxSigops @3 (context: Proxy.Context) -> (result: List(Int64));
-    getCoinbaseTx @4 (context: Proxy.Context) -> (result: Data);
-    getCoinbaseCommitment @5 (context: Proxy.Context) -> (result: Data);
-    getWitnessCommitmentIndex @6 (context: Proxy.Context) -> (result: Int32);
-    getCoinbaseMerklePath @7 (context: Proxy.Context) -> (result: List(Data));
-    submitSolution@8 (context: Proxy.Context, version: UInt32, timestamp: UInt32, nonce: UInt32, coinbase :Data) -> (result: Bool);
+    destroy @0 (context :Proxy.Context) -> ();
+    getBlockHeader @1 (context: Proxy.Context) -> (result: Data);
+    getBlock @2 (context: Proxy.Context) -> (result: Data);
+    getTxFees @3 (context: Proxy.Context) -> (result: List(Int64));
+    getTxSigops @4 (context: Proxy.Context) -> (result: List(Int64));
+    getCoinbaseTx @5 (context: Proxy.Context) -> (result: Data);
+    getCoinbaseCommitment @6 (context: Proxy.Context) -> (result: Data);
+    getWitnessCommitmentIndex @7 (context: Proxy.Context) -> (result: Int32);
+    getCoinbaseMerklePath @8 (context: Proxy.Context) -> (result: List(Data));
+    submitSolution @9 (context: Proxy.Context, version: UInt32, timestamp: UInt32, nonce: UInt32, coinbase :Data) -> (result: Bool);
 }
 
 struct BlockCreateOptions $Proxy.wrap("node::BlockCreateOptions") {