Move src/legacy/server/index_patterns to data plugin (server)

[lukeelmers]

• Remove any direct calls to _fields_for_wildcard and _fields_for_time_pattern routes and replace with usages of IndexPatternsService (server), or index_patterns_api_client (client).
• Convert errors.js to TS
• Convert resolve_time_pattern.js to TS
• Update routes to register with core.http & convert to TS
• [ ] Leave behind legacy indexPatternsServiceFactory for backwards compatibility, and instead look into whether we can replace this by providing a scoped instance of IndexPatternsService via the handler context pattern, available in the core.context service
• Delete src/legacy/server/index_patterns as it should no longer be in use anywhere in Kibana (and of course triple check that this is correct).

Part of #43438

[elasticmachine]

Pinging @elastic/kibana-app-arch

[sainthkh]

Most of the TODOs are done. One thing left is half of the last TODO "whether we can replace this by providing a scoped instance of IndexPatternsService via the handler context pattern, available in the core.context service."

I left that out because currently we cannot be sure that is necessary for plugins and services.

[lizozom]

@sainthkh I think there are also a few calls for the _fields_for_wildcard API left.
Or am I missing something?

[sainthkh]

@lizozom You're right. There's only one case left in x-pack/rollup. It's calling the API directly inside the server-side code.

It can be removed when we can import IndexPatternsFetcher from data plugin. Because IndexPatternsFetcher depends on ElasticSearch, I guess it is hard to do that now. (As far as I know, there is nothing like public/legacy.ts in server-side of kibana. Right?)

Note: When you search _fields_for_wildcard, there are other results. They don't have to be changed because they're for IndexPatternsAPIClient or integration tests.

[lukeelmers]

There's only one case left in x-pack/rollup. It's calling the API directly inside the server-side code.

It can be removed when we can import IndexPatternsFetcher from data plugin

Now that #55606 is merged, I believe we can safely remove src/legacy/server/index_patterns.