StringUtil: More Wrappers For <cctype>

`Common::IsLower(char)` was omitted as nothing needed it.

Source/Core/Common/StringUtil.h

@@ -275,6 +275,21 @@ inline bool IsAlpha(char c)
   return std::isalpha(c, std::locale::classic());
 }
 
+inline bool IsAlnum(char c)
+{
+  return std::isalnum(c, std::locale::classic());
+}
+
+inline bool IsUpper(char c)
+{
+  return std::isupper(c, std::locale::classic());
+}
+
+inline bool IsXDigit(char c)
+{
+  return std::isxdigit(c /* no locale needed */) != 0;
+}
+
 inline char ToLower(char ch)
 {
   return std::tolower(ch, std::locale::classic());

Source/Core/Core/Config/DefaultLocale.cpp

@@ -79,11 +79,9 @@ static DiscIO::Language ComputeDefaultLanguage()
 
 static std::optional<std::string> TryParseCountryCode(const std::string& locale)
 {
-  const auto is_upper = [](char c) { return std::isupper(c, std::locale::classic()); };
-
   for (const std::string& part : SplitString(locale, '-'))
   {
-    if (part.size() == 2 && is_upper(part[0]) && is_upper(part[1]))
+    if (part.size() == 2 && Common::IsUpper(part[0]) && Common::IsUpper(part[1]))
       return part;
   }
 

Source/Core/Core/IOS/ES/NandUtils.cpp

@@ -79,8 +79,7 @@ static bool IsValidPartOfTitleID(const std::string& string)
 {
   if (string.length() != 8)
     return false;
-  return std::all_of(string.begin(), string.end(),
+  return std::all_of(string.begin(), string.end(), Common::IsXDigit);
-                     [](const auto character) { return std::isxdigit(character) != 0; });
 }
 
 static std::vector<u64> GetTitlesInTitleOrImport(FS::FileSystem* fs, const std::string& titles_dir)

Source/Core/Core/Movie.cpp

@@ -93,7 +93,7 @@ static std::array<u8, 20> ConvertGitRevisionToBytes(const std::string& revision)
 {
   std::array<u8, 20> revision_bytes{};
 
-  if (revision.size() % 2 == 0 && std::all_of(revision.begin(), revision.end(), ::isxdigit))
+  if (revision.size() % 2 == 0 && std::all_of(revision.begin(), revision.end(), Common::IsXDigit))
   {
     // The revision string normally contains a git commit hash,
     // which is 40 hexadecimal digits long. In DTM files, each pair of

Source/Core/DiscIO/DiscUtils.cpp

@@ -13,6 +13,7 @@
 
 #include "Common/CommonTypes.h"
 #include "Common/MathUtil.h"
+#include "Common/StringUtil.h"
 #include "DiscIO/Blob.h"
 #include "DiscIO/Filesystem.h"
 #include "DiscIO/Volume.h"
@@ -39,8 +40,7 @@ std::string NameForPartitionType(u32 partition_type, bool include_prefix)
                                       static_cast<char>((partition_type >> 16) & 0xFF),
                                       static_cast<char>((partition_type >> 8) & 0xFF),
                                       static_cast<char>(partition_type & 0xFF)};
-    if (std::all_of(type_as_game_id.cbegin(), type_as_game_id.cend(),
+    if (std::all_of(type_as_game_id.cbegin(), type_as_game_id.cend(), Common::IsAlnum))
-                    [](char c) { return std::isalnum(c, std::locale::classic()); }))
     {
       return include_prefix ? "P-" + type_as_game_id : type_as_game_id;
     }

Source/Core/DolphinQt/Settings/USBDeviceAddToWhitelistDialog.cpp

@@ -30,8 +30,7 @@ static bool IsValidUSBIDString(const std::string& string)
 {
   if (string.empty() || string.length() > 4)
     return false;
-  return std::all_of(string.begin(), string.end(),
+  return std::all_of(string.begin(), string.end(), Common::IsXDigit);
-                     [](const auto character) { return std::isxdigit(character) != 0; });
 }
 
 USBDeviceAddToWhitelistDialog::USBDeviceAddToWhitelistDialog(QWidget* parent) : QDialog(parent)