refactor: Remove gArgs access from validation.cpp

This is done in the context of the libbitcoinkernel project, wherein
reliance of libbitcoinkernel code on the global gArgs is incrementally
removed.

Author: TheCharlatan

src/validation.cpp

@@ -11,7 +11,6 @@
 #include <arith_uint256.h>
 #include <chain.h>
 #include <checkqueue.h>
-#include <common/args.h>
 #include <consensus/amount.h>
 #include <consensus/consensus.h>
 #include <consensus/merkle.h>
@@ -2500,7 +2499,7 @@ bool Chainstate::FlushStateToDisk(
         // Write blocks and block index to disk.
         if (fDoFullFlush || fPeriodicWrite) {
             // Ensure we can write block index
-            if (!CheckDiskSpace(gArgs.GetBlocksDirPath())) {
+            if (!CheckDiskSpace(m_blockman.m_opts.blocks_dir)) {
                 return AbortNode(state, "Disk space is too low!", _("Disk space is too low!"));
             }
             {
@@ -2536,7 +2535,7 @@ bool Chainstate::FlushStateToDisk(
             // twice (once in the log, and once in the tables). This is already
             // an overestimation, as most will delete an existing entry or
             // overwrite one. Still, use a conservative safety factor of 2.
-            if (!CheckDiskSpace(gArgs.GetDataDirNet(), 48 * 2 * 2 * CoinsTip().GetCacheSize())) {
+            if (!CheckDiskSpace(m_chainman.m_options.datadir, 48 * 2 * 2 * CoinsTip().GetCacheSize())) {
                 return AbortNode(state, "Disk space is too low!", _("Disk space is too low!"));
             }
             // Flush the chainstate (which may refer to block index entries).