Fix: save_state! should only modify state field

What does this MR do and why?

Why: save_state! is overwriting fields other than state causing the migration document to lose name, started_at, fields during execution

What:

• only write out state field but keep everything else in the document
• defines the name field for the migration mapping (it was causing test failures)
• fix rubocop violations
• update specs to move off elastic_clean to elastic_delete_by_query trait, reduced test runtime locally from 15 minutes to 1.5 minutes. I chose elastic_delete_by_query to avoid flaky tests. The flaky tests were due to not cleaning up the indexed documents between example runs.

Screenshots or screen recordings

N/A

before (:elastic_clean)

➜ be rspec ee/spec/models/elastic/migration_record_spec.rb
Run options: include {:focus=>true}

All examples were filtered out; ignoring {:focus=>true}

Test environment set up in 6.63073 seconds
....................................

Finished in 22 minutes 58 seconds (files took 15.19 seconds to load)
36 examples, 0 failures

after (:elastic_delete_by_query)

❯ be rspec ee/spec/models/elastic/migration_record_spec.rb
Run options: include {:focus=>true}

All examples were filtered out; ignoring {:focus=>true}

Test environment set up in 6.667638 seconds
....................................

Finished in 1 minute 6.14 seconds (files took 14.39 seconds to load)
36 examples, 0 failures

How to set up and validate locally

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