scripted-diff: use TryGetTotalRam

Use the `Try` prefix to make failed RAM detection visible at call sites.

-BEGIN VERIFY SCRIPT-
git grep -q 'TryGetTotalRam' -- src && echo "Error: TryGetTotalRam already exists in src" && exit 1
git grep -l 'GetTotalRAM' -- src | xargs perl -pi -e 's/\bGetTotalRAM\b/TryGetTotalRam/g'
-END VERIFY SCRIPT-

src/node/caches.cpp

@@ -40,7 +40,7 @@ namespace node {
 uint64_t GetDefaultDBCache()
 {
     if constexpr (sizeof(void*) >= 8) {
-        if (GetTotalRAM().value_or(0) >= HIGH_DEFAULT_DBCACHE_MIN_TOTAL_RAM) {
+        if (TryGetTotalRam().value_or(0) >= HIGH_DEFAULT_DBCACHE_MIN_TOTAL_RAM) {
             return HIGH_DEFAULT_DBCACHE;
         }
     }
@@ -88,7 +88,7 @@ CacheSizes CalculateCacheSizes(const ArgsManager& args, size_t n_indexes)
 
 void LogOversizedDbCache(const ArgsManager& args) noexcept
 {
-    if (const auto total_ram{GetTotalRAM()}) {
+    if (const auto total_ram{TryGetTotalRam()}) {
         const uint64_t db_cache{CalculateDbCacheBytes(args)};
         if (ShouldWarnOversizedDbCache(db_cache, *total_ram)) {
             InitWarning(bilingual_str{tfm::format(_("A %zu MiB dbcache may be too large for a system memory of only %zu MiB."),