Improve assignability to target conditional types types that distribute with any/unknown extendsType

[Andarist]

fixes #60815

[Andarist]

This isn't correct as it removes those correct errors:

function f5<T>(t1: { x: T; y: T }, t2: T extends any ? { x: T; y: T } : never) {
  t1 = t2; // OK
  t2 = t1; // should fail
}

function f6<T>(t1: { x: T; y: T }, t2: T extends unknown ? { x: T; y: T } : never) {
  t1 = t2; // OK
  t2 = t1; // should fail
}