feat: move File.stat to Stat.path and update all references across docs, source, and tests

test/io/file/stat_static_nonexistent.wren

@@ -1,3 +0,0 @@
-import "io" for File
-
-File.stat("nonexistent") // expect runtime error: no such file or directory

test/io/stat/path.wren

@@ -1,7 +1,7 @@
-import "io" for File, Stat
+import "io" for Stat
 import "scheduler" for Scheduler
 
-var stat = File.stat("test/io/file/file.txt")
+var stat = Stat.path("test/io/file/file.txt")
 
 System.print(stat is Stat)            // expect: true
 System.print(stat.device is Num)      // expect: true

test/io/stat/path_directory.wren

@@ -1,7 +1,7 @@
-import "io" for File, Stat
+import "io" for Stat
 import "scheduler" for Scheduler
 
-var stat = File.stat("test/io/directory/dir")
+var stat = Stat.path("test/io/directory/dir")
 
 System.print(stat is Stat)            // expect: true
 System.print(stat.device is Num)      // expect: true

test/io/stat/path_nonexistent.wren

@@ -0,0 +1,3 @@
+import "io" for Stat
+
+Stat.path("nonexistent") // expect runtime error: no such file or directory