[8.x] Re-add update from support for PostgreSQL

[driesvints]

This PR re-introduces "update ... from ..." support for the PostgreSQL grammar. Since there wasn't a good option or straight way to re-implement the behavior after the refactor in #29393 I opted to add a new dedicated updateFrom method specifically for the PostgreSQL grammar.

This implementation is a bit cumbersome and crude as people will need to specifically use updateFrom instead of update if they want the correct behavior. Ideally this would be done automatically.

I've tested this with the queries from #33265 and got them back working with this. I also re-added the original tests that were removed.

Before merging this I'd like to:

• Get a review from @staudenmeir
• Get feedback from people who reported Postgresql update: removed support for "update ... from ..." statement in 6.x and 7.x #33265
• Maybe clean up the code in the PostgreSQL grammar

If we get feedback from someone who can think of a better way to solve this then gladly. Otherwise I think this is the only solution for the problem at hand.

Fixes #33265

[mikerockett]

Thanks for this! I wonder if updateWith might be better suited?

updateFrom works though, and another option I'd thought of, updateUsing, would also make sense, but I thing the "using" terminology is better for callables.

[driesvints]

@mikerockett I personally think updateFrom is probably the most straightforward name since that indicates the fix its making.

One other thing that might be considered is changing the API of the method slightly so the name makes more sense or its usage is more straightforward.

[driesvints]

Since no one from the related issue has replied to far I'm submitting this as-is.

[hyde1]

Hi @driesvints!
Thanks for working on this issue. I just gave a try and it works perfectly for me and my use case.