Replace Gut with WAT

Gut was freezing on some integration tests. It was also entering an
infinite loop after exiting (even after closing Godot and VSCode) which
caused a `godot.log` file in app_userdata to keep growing until my hard
drive was full.

test/integration/uv_utils.test.gd

@@ -0,0 +1,31 @@
+extends WAT.Test
+
+const LibuvUtils = preload("res://addons/godot_xterm/nodes/pty/libuv_utils.gd")
+
+const EMPTY_VAR = "GODOT_XTERM_TEST_EMPTY_ENV_VAR"
+const TEST_VAR = "GODOT_XTERM_TEST_ENV_VAR"
+const TEST_VAL = "TEST123"
+
+var env: Dictionary
+
+
+func pre():
+	assert(OS.set_environment(EMPTY_VAR, ""))
+	assert(OS.set_environment(TEST_VAR, TEST_VAL))
+	env = LibuvUtils.get_os_environ()
+
+
+func test_has_empty_var():
+	asserts.has(EMPTY_VAR, env)
+
+
+func test_empty_var_has_empty_val():
+	asserts.is_equal(env[EMPTY_VAR], "")
+
+
+func test_has_test_var():
+	asserts.has(TEST_VAR, env)
+
+
+func test_test_var_has_correct_val():
+	asserts.is_equal(env[TEST_VAR], TEST_VAL)