## Summary
Fix https://github.com/elastic/kibana/issues/217923
Investigations in https://github.com/elastic/kibana/issues/217368 showed
that there was basically no performance impact to passing the AST across
a thread boundary. But we also didn't detect a pressing reason to remove
the worker.
Since then, however, we noticed another cost associated with the worker:
it's a hefty Javascript file, even in production builds. In addition, we
are doing parsing on the main thread _and_ the worker, so the
`kbn-esql-ast` package is actually being loaded and parsed twice by the
browser, once for the main thread and once for the worker.
This PR removes our worker. Our parsing associated with validation and
autocomplete will still be done asynchronously, but on the main thread.
I do not see any regression in perceived performance.
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Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>
Co-authored-by: Stratoula Kalafateli <efstratia.kalafateli@elastic.co>
## Summary
Cleanups the implementation of the metadata logic. There is no reason at
this point (and maybe not even in the future) to have this metadata list
be dynamic. This PR is removing this logic and cleans it up
