Don't load all sync states when page slice is empty

Created by: eseliger

When the list of IDs is empty, the store will just attempt to load all changeset sync states, which takes some time, depending on the count of changesets. This made queries for empty page slices be way slower than for non-empty ones.

Created by: sourcegraph-bot

Notifying subscribers in CODENOTIFY files for diff b95992a93f26231427b7ec0bca5d0dc5df74065e...78675e78e0fcff894407d437ffd231261fd2265f.

Notify	File(s)
@LawnGnome	enterprise/internal/campaigns/resolvers/changeset_apply_preview_connection.go enterprise/internal/campaigns/resolvers/changeset_connection.go

Created by: codecov[bot]

Codecov Report

Merging #17707 (78675e7) into main (b95992a) will increase coverage by 0.00%. The diff coverage is 58.33%.

@@           Coverage Diff           @@
##             main   #17707   +/-   ##
=======================================
  Coverage   51.19%   51.19%           
=======================================
  Files        1720     1720           
  Lines       86034    86038    +4     
  Branches     7764     7764           
=======================================
+ Hits        44042    44045    +3     
+ Misses      38102    38101    -1     
- Partials     3890     3892    +2     

Flag	Coverage Δ		*Carryforward flag
go	49.93% <58.33%> (+<0.01%)
integration	30.73% <ø> (ø)		Carriedforward from b95992a
storybook	30.62% <ø> (ø)		Carriedforward from b95992a
typescript	54.24% <ø> (ø)		Carriedforward from b95992a
unit	34.60% <ø> (ø)		Carriedforward from b95992a

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

Impacted Files	Coverage Δ
...ns/resolvers/changeset_apply_preview_connection.go	51.61% <50.00%> (-0.03%)
...ternal/campaigns/resolvers/changeset_connection.go	70.37% <66.66%> (+1.13%)
...prise/cmd/frontend/auth/httpheader/config_watch.go	50.00% <0.00%> (-33.34%)
...nal/campaigns/resolvers/changeset_apply_preview.go	65.18% <0.00%> (+0.74%)
...nterprise/cmd/frontend/auth/httpheader/provider.go	20.00% <0.00%> (+20.00%)