Replace most Combine based APIs with new async versions

[roanutil]

Subscription endpoints will hopefully change to use AsyncSequence for async support but are still using Combine for now.

[codecov-commenter]

Codecov Report

Merging #7 (c560229) into main (12fe604) will decrease coverage by 5.17%.
The diff coverage is 80.81%.

@@            Coverage Diff             @@
##             main       #7      +/-   ##
==========================================
- Coverage   77.65%   72.48%   -5.18%     
==========================================
  Files          11       13       +2     
  Lines         555      556       +1     
==========================================
- Hits          431      403      -28     
- Misses        124      153      +29     

Impacted Files	Coverage Δ
...ources/CoreDataRepository/Result+CRUDHelpers.swift	32.14% <45.00%> (-54.82%)	⬇️
...reDataRepository/NSManagedObject+CRUDHelpers.swift	75.00% <75.00%> (ø)
...Repository/NSManagedObjectContext+Scratchpad.swift	48.48% <78.57%> (-14.68%)	⬇️
...eDataRepository/CoreDataRepository+Aggregate.swift	91.11% <80.64%> (+3.35%)	⬆️
.../CoreDataRepository/CoreDataRepository+Batch.swift	80.48% <80.83%> (-2.50%)	⬇️
...epository/NSManagedObjectContext+CRUDHelpers.swift	83.33% <83.33%> (ø)
...eDataRepository/NSManagedObjectContext+Child.swift	93.33% <90.00%> (-6.67%)	⬇️
...s/CoreDataRepository/CoreDataRepository+CRUD.swift	91.25% <100.00%> (-4.67%)	⬇️
.../CoreDataRepository/CoreDataRepository+Fetch.swift	89.79% <100.00%> (ø)
... and 2 more

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