refactor(sync): use task scheduler

[eusebiu-constantin-petu-dbk]

What type of PR is this?

Which issue does this PR fix:

What does this PR do / Why do we need it:

If an issue # is not available please add repro steps and logs showing the issue:

Testing done on this change:

Automation added to e2e:

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[eusebiu-constantin-petu-dbk]

todo:

1. reload sync config
2. rebase laurentiu changes for repodb

fixed

[codecov]

Codecov Report

Merging #1301 (e0a5c18) into main (e148343) will increase coverage by 0.10%.
The diff coverage is 91.88%.

@@            Coverage Diff             @@
##             main    #1301      +/-   ##
==========================================
+ Coverage   90.99%   91.10%   +0.10%     
==========================================
  Files         104      114      +10     
  Lines       22620    22726     +106     
==========================================
+ Hits        20583    20704     +121     
+ Misses       1518     1510       -8     
+ Partials      519      512       -7     

Impacted Files	Coverage Δ
pkg/extensions/sync/on_demand_disabled.go	0.00% <0.00%> (ø)
pkg/extensions/sync/remote.go	80.26% <80.26%> (ø)
pkg/extensions/sync/references/oras.go	82.60% <82.60%> (ø)
pkg/extensions/sync/references/oci.go	83.76% <83.76%> (ø)
pkg/common/common.go	94.11% <87.50%> (+0.05%)	⬆️
pkg/extensions/sync/references/cosign.go	90.90% <90.90%> (ø)
pkg/extensions/sync/local.go	91.32% <91.32%> (ø)
pkg/storage/local/local.go	81.83% <91.66%> (-0.14%)	⬇️
pkg/extensions/sync/oci_layout.go	91.89% <91.89%> (ø)
pkg/extensions/sync/sync.go	91.17% <92.59%> (-3.67%)	⬇️
... and 11 more

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[rchincha]

When syncing to an existing local repo, we may clobber "latest", do sane things and log

[rchincha]

For a given/existing repo, sync and clients may both be writers to the same repo, so locking?

[rchincha]

Recursive download of references (I expect two levels)

[rchincha]

lgtm