Replace identity equality with Object.is in toBe matcher

[mkubilayk]

Summary

This replaces the strict equality (===) check with Object.is in the toBe matcher. Object.is works exactly the same as triple equals except:

> Object.is(NaN, NaN)
true
> NaN === NaN
false

> Object.is(-0, +0)
false
> -0 === +0
true

Hence, this allows us to fix #4907.

Test plan

Added two tests for toBe matcher. I couldn't test the docs due to #4911 and #4912, but changes are trivial.

[codecov-io]

Codecov Report

Merging #4917 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4917   +/-   ##
=======================================
  Coverage   59.98%   59.98%           
=======================================
  Files         198      198           
  Lines        6563     6563           
  Branches        4        4           
=======================================
  Hits         3937     3937           
  Misses       2626     2626

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[cpojer]

This is great! Thank you so much.

[SimenB]

This needs an entry in the changelog (in general, all should be there, but this in particular is a breaking change, so should definitely be there). @mkubilayk wanna send a PR for it?

[mkubilayk]

@SimenB sure, will send it today.

[mkubilayk]

@SimenB #5043.

[github-actions]

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