authz: remove upsert for updating user pending permissions

Created by: unknwon

We used to rely on ON CONFLICT ON CONSTRAINT to do upsert when we do batch update on user_pending_permissions table. However, there are reasons why the approach in this PR is better (use update not upsert):

1. The primary key (id) of user_pending_permissions table is increased rapidly every time hits ON CONFLICT ON CONSTRAINT for no obvious benefit. (Have seen a customer with few thousand rows but MAX(id) >80,000,000).
2. At the moment of "upsert", we already have ids on hand, could have just used it to directly update rows with these ids as they are primary keys.

This PR does not solve 1. entirely but at least slows down id increment pace by half. Another half is caused by:

https://github.com/sourcegraph/sourcegraph/blob/e0145db0159fad19a1f48735a27986e502cbf3c9/enterprise/internal/db/perms_store.go#L598-L599

Created by: codecov[bot]

Codecov Report

Merging #13592 into main will decrease coverage by 0.35%. The diff coverage is 80.00%.

@@            Coverage Diff             @@
##             main   #13592      +/-   ##
==========================================
- Coverage   51.79%   51.43%   -0.36%     
==========================================
  Files        1503     1503              
  Lines       84134    83371     -763     
  Branches     6910     6910              
==========================================
- Hits        43573    42885     -688     
+ Misses      36924    36888      -36     
+ Partials     3637     3598      -39     

Flag	Coverage Δ		*Carryforward flag
#go	52.61% <80.00%> (-0.47%)
#integration	29.63% <ø> (ø)		Carriedforward from 9791957
#typescript	48.25% <ø> (ø)		Carriedforward from 9791957
#unit	33.94% <ø> (ø)		Carriedforward from 9791957

*This pull request uses carry forward flags. Click here to find out more.

Impacted Files	Coverage Δ
enterprise/internal/db/perms_store.go	78.67% <80.00%> (+0.03%)
cmd/repo-updater/repos/syncer.go	59.32% <0.00%> (-17.18%)
internal/db/dbutil/dbutil.go	14.44% <0.00%> (-6.16%)
internal/trace/httptrace.go	6.06% <0.00%> (-2.28%)
cmd/repo-updater/repos/store.go	84.32% <0.00%> (-2.09%)
cmd/repo-updater/repos/types.go	76.20% <0.00%> (-1.75%)
cmd/repo-updater/repos/observability.go	92.73% <0.00%> (-0.91%)
cmd/frontend/graphqlbackend/zoekt.go	76.08% <0.00%> (-0.82%)
internal/db/external_services.go	61.61% <0.00%> (-0.71%)
cmd/repo-updater/repos/sync_worker.go	90.32% <0.00%> (-0.35%)
... and 758 more

Created by: unknwon

Thanks again @eseliger and @daxmc99 for pair reviewing with me! Merging