Unparenthesized SubSelect as FromItem

[ssteinhauser]

As already stated in my first contribution to this project, I'd like to implement some features for Exasol DBMS.
The first thing was to support unparenthesized sub selects (see #2046).

However, one related feature is still open for discussion: support of unparenthesized sub select as FromItem

I've had a look at LateralSubSelect, but I think to support the complete syntax of the feature flagged unparenthesised Select() as FromItem, the Select class would have to implement the FromItem interface and I would have to implement the methods of FromItem in all sub classes which are extending Select.
Before I go ahead and do the implementation I would like to ask for your opinion on this. Do you agree with it or do you have another suggestion.

Originally posted by @ssteinhauser in #2046 (comment)

I'd like to discuss this topic here to work out a solution I could implement then.

[manticore-projects]

Greetings and welcome back.

Please just go ahead, I would be here in case of any questions. Cheers!

[ssteinhauser]

Alright, thank you. I've just provided a PR (#2073) - please let me know your thoughts.

[ssteinhauser]

Discussion is closed with PR #2073