Everywhere: Use LibFileSystem where trivial

Author: https://github.com/cammo1123
Commit: 1d24f394c6
Pull-request: https://github.com/SerenityOS/serenity/pull/17789
Reviewed-by: https://github.com/AtkinsSJ
Reviewed-by: https://github.com/caoimhebyrne
Reviewed-by: https://github.com/kleinesfilmroellchen ✅
Reviewed-by: https://github.com/linusg
Reviewed-by: https://github.com/pascalpuffke
Reviewed-by: https://github.com/timschumi ✅

Userland/Libraries/LibTest/JavaScriptTestRunnerMain.cpp

@@ -8,6 +8,7 @@
 
 #include <LibCore/ArgsParser.h>
 #include <LibCore/DeprecatedFile.h>
+#include <LibFileSystem/FileSystem.h>
 #include <LibTest/JavaScriptTestRunner.h>
 #include <signal.h>
 #include <stdio.h>
@@ -158,7 +159,7 @@ int main(int argc, char** argv)
         common_path = DeprecatedString::formatted("{}/Userland/Libraries/LibJS/Tests/test-common.js", serenity_source_dir);
 #endif
     }
-    if (!Core::DeprecatedFile::is_directory(test_root)) {
+    if (!FileSystem::is_directory(test_root)) {
         warnln("Test root is not a directory: {}", test_root);
         return 1;
     }