feat: add File.stat static method and test for directory stat

Add a new `File.stat(path)` static method that returns a `Stat` object with low-level file system metadata for both files and directories. Include a test file `stat_static_directory.wren` that validates the returned `Stat` object's type and field types (device, inode, mode, linkCount, user, group, specialDevice, size, blockSize, blockCount) against a known test directory.

test/io/file/stat_static_directory.wren

@@ -0,0 +1,16 @@
+import "io" for File, Stat
+import "scheduler" for Scheduler
+
+var stat = File.stat("test/io/directory/dir")
+
+System.print(stat is Stat)            // expect: true
+System.print(stat.device is Num)      // expect: true
+System.print(stat.inode is Num)       // expect: true
+System.print(stat.mode is Num)        // expect: true
+System.print(stat.linkCount)          // expect: 5
+System.print(stat.user is Num)        // expect: true
+System.print(stat.group is Num)       // expect: true
+System.print(stat.specialDevice)      // expect: 0
+System.print(stat.size)               // expect: 170
+System.print(stat.blockSize is Num)   // expect: true
+System.print(stat.blockCount is Num)  // expect: true