Bidirectional comparable relation for primitive types

[ahejlsberg]

This PR makes the comparable relation bidirectional for primitive types. For example, the following previously was an error but is now permitted:

declare const x: { a: 1, b: string };
declare const y: { a: number, b: 'a' };

x === y;  // Now ok, previously was error

[sandersn]

typo:independently

[weswigham]

Given how similar the logic in two replaced callsites for isSimpleTypeRelatedTo is, it'd be nice to see the logic moved into a helper function; but it's not required, since it's only duplicating code in two places. 🤷‍♂️