Convert QP to MLv2 Part 2 (#39824)

* Keep fetch_source_query.clj

* Copy fetch_source_query.clj into fetch_source_query_legacy.clj

* Set back fetch_source_query.clj file

* Convert QP to MLv2, part 1

* Keep legacy implementation around for time being

* Port thru convert-to-legacy

* expand-macros is converted to legacy

* Test fixes 

* Test fixes and better keys

* Test fixes

* Test fixes 

* More test fixes 

* Test fix? 

* Wow, maybe I finally fixed everything 

* Last few test fixes 

* PR feedback; lib.walk should support splicing in multiple replacement stages

* Update fetch-source-query to use improved lib.walk

* Have I fixed everything now? 

* Remove stray println

* Another MongoDB fix 

* Convert QP to MLv2 Part 2

* Remove most of the fetch-source-query-legacy stuff

* Remove the changes to expand-macros for now, we can do that in a follow-on PR.

* Test fix

* Test fix

* TEST FIXES?! 

* Kondo & test fixes

* Oops, make sure we have the updated tests

* Fixes 

* Test fixes 

* Convert resolve-source-table

* Appease Kondo

* Unparallelize the tests

* Another test that shouldn't be parallel

* Make tests more robust

* Test fixes