Document Loki connector result types

[jeschkies]

Description

The original Loki connector release was missing a description of the result types of a metric query. This changes adds them.

Release notes

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## Section
* Fix some things. ({issue}`issuenumber`)

[jeschkies]

I'm unsure how you would like to have the types documented. I've used the DESCRIBE OUTPUT query and result now. It's a little verbose IMHO. It would help if you could point me to an example on how to document the output type.

[mosabua]

A list-table similar to

https://github.com/trinodb/trino/blob/master/docs/src/main/sphinx/connector/postgresql.md?plain=1#L136

and we dont need the example query but if you want to keep it thats fine as well. Just add it after the table.

[ebyhr]

I don't think we should add another list-table. We already have https://trino.io/docs/current/connector/loki.html#loki-to-trino-type-mapping

[mosabua]

I don't think we should add another list-table. We already have https://trino.io/docs/current/connector/loki.html#loki-to-trino-type-mapping

Oh .. I totally forgot .. what is the PR trying to achieve then @jeschkies .. seems like all the needed info is there already.

Maybe we just need to tweak the wording in the title of that table and add some more info there.

[mosabua]

I chatted with @jeschkies as part of the TCB work .. I think we can close this PR .. can you confirm @jeschkies ?

[ebyhr]

Please feel free to reopen if you continue the work.