Recovered some integration tests

Created by: maxsbelt

I noticed that all the latest PRs have a red cross (even merged). This PR contains several fixes that recover some of integration tests:

jest/no-conditional-expect rule

Fix https://github.com/facebook/create-react-app/pull/10091/commits/4bcf5989f0c3fb45a376ebaa9814a8c73659dcfd.

jest version inconsistency

Fix https://github.com/facebook/create-react-app/pull/10091/commits/fc4c396914d8ede89156b11990e6298b1bdaea8a.

untracked .eslintcache file

Will be fixed by https://github.com/facebook/create-react-app/pull/10177.

missing React in tests after eject

Fix https://github.com/facebook/create-react-app/pull/10091/commits/7b8c760dfe9e314fdef66efd5a1bd05eb1751091.

src regex issue

Introduced by https://github.com/facebook/create-react-app/pull/9516. The encoded version of the optimized image ends with k=.

Fix https://github.com/facebook/create-react-app/pull/10091/commits/fe5fbeeceab69c4fbb05cc6c18da0e249ea2f2df.