refactor, BlockManager: Replace fastprune from arg with options

Remove access to the global gArgs for the fastprune argument and
replace it by adding a field to the existing BlockManager Options
struct.

When running `clang-tidy-diff` on this commit, there is a diagnostic
error: `unknown type name 'uint64_t' [clang-diagnostic-error] uint64_t
prune_target{0};`, which is fixed by including cstdint.

This should eventually allow users of the BlockManager to not rely on
the global gArgs and instead pass in their own options.

Author: TheCharlatan

src/kernel/blockmanager_opts.h

@@ -5,6 +5,8 @@
 #ifndef BITCOIN_KERNEL_BLOCKMANAGER_OPTS_H
 #define BITCOIN_KERNEL_BLOCKMANAGER_OPTS_H
 
+#include <cstdint>
+
 class CChainParams;
 
 namespace kernel {
@@ -16,6 +18,7 @@ namespace kernel {
 struct BlockManagerOpts {
     const CChainParams& chainparams;
     uint64_t prune_target{0};
+    bool fast_prune{false};
 };
 
 } // namespace kernel

src/node/blockmanager_args.cpp

@@ -31,6 +31,8 @@ std::optional<bilingual_str> ApplyArgsManOptions(const ArgsManager& args, BlockM
     }
     opts.prune_target = nPruneTarget;
 
+    if (auto value{args.GetBoolArg("-fastprune")}) opts.fast_prune = *value;
+
     return std::nullopt;
 }
 } // namespace node

src/node/blockstorage.cpp

@@ -581,7 +581,7 @@ void BlockManager::UnlinkPrunedFiles(const std::set<int>& setFilesToPrune) const
 
 FlatFileSeq BlockManager::BlockFileSeq() const
 {
-    return FlatFileSeq(gArgs.GetBlocksDirPath(), "blk", gArgs.GetBoolArg("-fastprune", false) ? 0x4000 /* 16kb */ : BLOCKFILE_CHUNK_SIZE);
+    return FlatFileSeq(gArgs.GetBlocksDirPath(), "blk", m_opts.fast_prune ? 0x4000 /* 16kb */ : BLOCKFILE_CHUNK_SIZE);
 }
 
 FlatFileSeq BlockManager::UndoFileSeq() const
@@ -619,7 +619,7 @@ bool BlockManager::FindBlockPos(FlatFilePos& pos, unsigned int nAddSize, unsigne
         unsigned int max_blockfile_size{MAX_BLOCKFILE_SIZE};
         // Use smaller blockfiles in test-only -fastprune mode - but avoid
         // the possibility of having a block not fit into the block file.
-        if (gArgs.GetBoolArg("-fastprune", false)) {
+        if (m_opts.fast_prune) {
             max_blockfile_size = 0x10000; // 64kiB
             if (nAddSize >= max_blockfile_size) {
                 // dynamically adjust the blockfile size to be larger than the added size