[Lens] [7.7] Migration for 7.7

[wylieconlon]

When loading a saved XY Lens visualization that was created pre-7.7, such as bar chart, line chart, or area chart, the configuration panel on the right would show empty dimensions like this:

The bug was caused by a change to how dimensions are represented that I introduced in #58279

Instead of fixing the bug in the runtime, this is fixing the bug using a migration. After 7.7 was branched from master, @timroes changed the way Lens saved objects were registered, so this PR can only target 7.7- another PR will target 7.8 and later

Fixes #61939

Replaces #62707

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 7ccd6e1

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[mbondyra]

I've tested the following configurations on Chrome, migrating from 7.6:

1. Single layer
   a. Date histogram on count
   b. Date histogram with multiple y axes and break down applied
   c. non-time X-axis and single Y axis
   d. non-time X-axis and multiple y axes and break down applied
2. Multiple layers
   a. two layers both of one date histogram of the same primary timefield on one index
   b. two layers of different X axes (time based and not time based) and multiple Y-axes
   c. two time-based visualizations on different index patterns

All works as expected migrating from 7.6 to this PR. 👏