Improve error message for == of two different types

[ghost]

Fixes #26592

[iliashkolyar]

@Andy-MS
If i'm not mistaken, this fix will not handle literal type comparisons such as:

var a = (1 == "1");
var b = ("" == 0);
var c = (false == "");
var d = (false == 0);

All of the above are also runtime comparisons that will yield "This condition will always return 'false'" mistakenly.

[ghost]

@DanielRosenwasser Please review

[elibarzilay]

I rebased it up the history in small steps, and it worked fine with obvious fixes, until 48fc6b8 (from #32239) which edits the same code to something different, so making this work will require actually redoing it. (It looks like the main issue is that 48fc6b8 extends tryGiveBetterPrimaryError whereas this one removes it.)

[elibarzilay]

Talked to @RyanCavanaugh, seems not worth the effort of reviving.