SQL: Types class refactoring

[astefan]

At the moment org.elasticsearch.xpack.sql.type.Types has code exclusively used in tests for testing JSON mappings' validity. The way a json containing an index mapping is loaded and interpreted, though, differs from the main code of ES SQL (residing in IndexResolver) and the algorithms are significantly different.
This means that, whenever the code in IndexResolver changes (for example - #51251), the code in Types needs to change as well which introduces an unnecessary maintenance task.

[elasticmachine]

Pinging @elastic/es-search (:Search/SQL)

[soarescaique]

Can I work on this?

[matriv]

Hi @soarescaique Thank you for your interest in contributing!
Inline with common open source practices, we would like to no longer block and attribute issues, but rather invite anyone with a concrete proposal to simply submit a PR. No one likes duplicating work, but please consider that chances of concurrent PRs are low - especially for longer standing issues - and quality will trump over submission order.

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)