Code cleanup, use pathlib, use pytest keyboard

Clean up checks and logics that are unnecessary due to MILC updates.
Use pathlib instead of os.path for readability.
Use the 'pytest' keyboard for the tests.
Add community layout for 'handwired/onekey/pytest' so we can test
community layouts.

layouts/community/ortho_1x1/layout.json

@@ -0,0 +1 @@
+[""]

layouts/community/ortho_1x1/test/keymap.c

@@ -0,0 +1,12 @@
+#include QMK_KEYBOARD_H
+
+/* This keyboard/layout is used to test community layout discovery/compilation. */
+
+#define _DEFAULT 0
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+
+[_DEFAULT] = LAYOUT (
+    KC_B
+),
+};