Add rule to detect invalid type literal assertions

[ajafff]

microsoft/TypeScript#14156

These are currently no compile error:

const True = false as true;
const one = 2 as 1;
const str = 'hello' as 'str';

declare const foo: 'foo';
foo as 'string';

declare const bar: 'foo' | 'bar';
bar as 'string';

// this should still be allowed:
bar as 'foo';

This only affects literals asserted to a different literal of the same widened type.

These are handled correctly:

1 as 'str';                    // Type 1 is not comparable to type "str"
['hello'] as ['str'];          // Type "hello" is not comparable to type "str"
({a: 'hello'} as {a: 'str'});  // Type "hello" is not comparable to type "str"