runtime(lua): add/subtract a 'shiftwidth' after '('/')' in indentexpr

Problem:

- Current lua indentexpr does not indent for '(' ')'.
- Missing indent test for lua.

Solution:

- Match '(', ')' in `function GetLuaIndentIntern`.
- Add an indent test for lua.

closes: #15364

Signed-off-by: Yinzuo Jiang <jiangyinzuo@foxmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/indent/testdir/lua.in

@@ -0,0 +1,19 @@
+-- vim: set ft=lua sw=2 noet:
+
+-- START_INDENT
+function foo(a, b, c, d)
+ return { a, b, c, d }
+end
+
+local a = foo(
+1,
+2,
+"longxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
+4
+)
+
+local b = {
+1,
+ 2,
+}
+-- END_INDENT

runtime/indent/testdir/lua.ok

@@ -0,0 +1,19 @@
+-- vim: set ft=lua sw=2 noet:
+
+-- START_INDENT
+function foo(a, b, c, d)
+  return { a, b, c, d }
+end
+
+local a = foo(
+  1,
+  2,
+  "longxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
+  4
+)
+
+local b = {
+  1,
+  2,
+}
+-- END_INDENT