Add MERGE to SQL support documentation

[jhlodin]

Description

Add links to the new SQL MERGE statement to the appropriate documentation

Is this change a fix, improvement, new feature, refactoring, or other?

Improvement

Is this a change to the core query engine, a connector, client library, or the SPI interfaces? (be specific)

Documentation

How would you describe this change to a non-technical end user or system administrator?

Document which connectors support SQL MERGE

Related issues, pull requests, and links

• Completes documentation added in https://github.com/trinodb/trino/pull/7933

Documentation

( ) No documentation is needed. (x) Sufficient documentation is included in this PR. ( ) Documentation PR is available with #prnumber. ( ) Documentation issue #issuenumber is filed, and can be handled later.

Release notes

(x) No release notes entries required. ( ) Release notes entries required with the following suggested text:

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

[mosabua]

So odd how this was implemented in the object storage connectors and kudu ..