Flink: Support create table like and source watermark for flink sql to 1.18,1.19

[swapna267]

Backporting changes in following PR's to Flink-1.18 and Flink-1.19

#12199
#12191

[pvary]

@swapna267: is this a clean backport?
For future backports, please create one backport PR for every PR on the main. People maintaining internal versions of Iceberg might want to have one set of changes on their branch, and might opt out from cherry picking another change. If we combine backports, we make their life harder.

[swapna267]

Oh ok. Was not aware of that. I merged 2 PR's into one, while backporting.

Will close this and create separate backport PR's corresponding to individual PR's. Thanks.

[swapna267]

As both PR's , 1.20 PR's #12199
#12191
are already merged into main, will it still be helpful to have separate backport PR's or can we have merged into one ?

[pvary]

I still prefer 1 by 1 backports.

[swapna267]

Sure.
Created new PR , #12679 for backporting #12199 . Once merged, will create next one, as there are overlapping changes.

[pvary]

Thanks for your understanding @swapna267 !