Fix 'space-before-function-paren' for anonymous/arrow generic functions

[ksvitkovsky]

PR checklist

• Addresses an existing issue: *space-before-function-paren* with async arrow function with generic type parameter #2308
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Fix considers the following cases as exceptions and skips whitespace check:

• arrow function with type parameters
• anonymous functions with type parameters

[Jameskmonger]

Will this fix the following case? I want it to be valid, but currently I get a lint issue.

const foo = <T>(a: T) => {};

[ajafff]

@Jameskmonger The added tests tell that your code snippet would be valid after this PR lands

[ajafff]

Thanks @ksvitkovsky

[Jameskmonger]

@hisuwh This fixes the issue you were talking about.