feat(linter/plugins): RuleTester support languageOptions.sourceType (#16660)

`RuleTester` use `languageOptions.sourceType` in config / test case definition to determine whether to parse a file as script or module.

* In standard mode, `sourceType: "unambiguous"` is also supported.
* In ESLint-compat mode, `sourceType: "commonjs"` is also supported (treated the same as `"script"`).

This fixes ~300 conformance tests.

Author: overlookmotel