kernel: De-globalize signature cache

Move its ownership to the ChainstateManager class.

Next to simplifying usage of the kernel library by no longer requiring
manual setup of the cache prior to using validation code, it also slims
down the amount of memory allocated by BasicTestingSetup.

Use this opportunity to make SignatureCache RAII styled

Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

src/kernel/chainstatemanager_opts.h

@@ -50,6 +50,7 @@ struct ChainstateManagerOpts {
     //! Number of script check worker threads. Zero means no parallel verification.
     int worker_threads_num{0};
     size_t script_execution_cache_bytes{DEFAULT_SCRIPT_EXECUTION_CACHE_BYTES};
+    size_t signature_cache_bytes{DEFAULT_SIGNATURE_CACHE_BYTES};
 };
 
 } // namespace kernel

src/kernel/validation_cache_sizes.h

@@ -1,19 +0,0 @@
-// Copyright (c) 2022 The Bitcoin Core developers
-// Distributed under the MIT software license, see the accompanying
-// file COPYING or http://www.opensource.org/licenses/mit-license.php.
-
-#ifndef BITCOIN_KERNEL_VALIDATION_CACHE_SIZES_H
-#define BITCOIN_KERNEL_VALIDATION_CACHE_SIZES_H
-
-#include <script/sigcache.h>
-
-#include <cstddef>
-#include <limits>
-
-namespace kernel {
-struct ValidationCacheSizes {
-    size_t signature_cache_bytes{DEFAULT_MAX_SIG_CACHE_BYTES / 2};
-};
-}
-
-#endif // BITCOIN_KERNEL_VALIDATION_CACHE_SIZES_H