worker_spi: Fix race condition in newly-added TAP tests
The second portion of the tests had a race condition where it would be
possible for the startup of the dynamic workers to fail, in the event
where the static workers started before them with the library loading in
shared_preload_libraries did not finish to create their respective
schemas. The conflict is caused by the fact that the dynamic and static
workers used the same IDs, overlapping each other, so, for now, switch
the dynamic workers to use different IDs, leading to different schemas
created.
Reported-by: Andres Freund
Discussion: https://postgr.es/m/
20230728022332.egqzobhskmlf6ntr@awork3.anarazel.de