Tests: Move Spectrum related tests to single test runner

[gziolo]

Part of #3942.

It contains:

• client/lib/cart-values
• client/lib/cart/store
• client/lib/credit-card-details
• client/lib/network-connection - library created during my trial :)
• client/lib/plans-list
• client/my-sites/upgrades/cart
• client/my-sites/upgrades/components/domain-warnings
• client/my-sites/upgrades/domain-search (moved to client/components/domains/domain-suggestion)

Testing

1. Open terminal.
2. Go to client folder.
3. Run make test.

[gziolo]

/cc @janm6k @blowery @aduth @mtias @nb

It looks like this PR contains most of standard refactorings necessary to migrate to single test runner. Last missing bits can be found in #3973 from @blowery which introduces new immutablyEqual helper and uses useMockery helper.

Let me list here common refactorings:

• remove sinonChai setup (it is now part of single runner setup)
• replace mockery setup with useMockery helper call
• replace require( 'lib/react-test-env-setup' )(); with useFakeDom helper call
• add useFilesystemMocks helper call whenever we override app files in tests
• chai-immutable is about to be removed, but we should promote using immutablyEqual helper

To consider:

• mirror test file name with file under test
• mirror test describe label with file name

Once we merge those 2 PRs we should write P2 summary post and ask for help all Calypso developers.

[janm6k]

👍 Nice!