esArchiver / migrations causing test flakiness

[rudolf]

Although esArchiver is deprecated in favour of kbnArchiver, core still uses it in several of our test suites because we need to be able to create hidden, non-importable saved objects and saved objects across several spaces.

Because esArchiver directly creates/deletes saved object system indices this interferes with migrations. This seems to be the underlying cause of all of the following skipped tests (see e.g. the investigation by @gsoldevila #131871 (comment)).

Note that some of these skipped tests are flaky on 7.x only and the migrations behaviour between 7.x and later 8.x is significantly different, so we might not be able to solve this with a single PR.

#160833
#147635
#132855
#132566
#131871
#131834
#131830
#131192
#130305
#127545

[elasticmachine]

Pinging @elastic/kibana-core (Team:Core)