[35244] changed the way that `WP_UnitTest_Generator_Sequence()` created an
incrementor for object fields (like 'post_name' and 'user_email'), by making
incrementor static across the entire run of the test suite. While this helped
to enforce uniqueness across the tests, it has the side effect of bumping the
incrementor between fields on the same object (so that, eg, the same post might
have `post_name` "post-12" but `post_title` "Post 13". By switching to a
technique that uses the same incrementor for each field belonging to a given
fixture, we conform better to the expectations of developers using
`WP_UnitTest_Factory`.
Fixes#35199.
git-svn-id: https://develop.svn.wordpress.org/trunk@37299 602fd350-edb4-49c9-b593-d223f7449a82