Add InsertProvider extensions and tests

[JimBobSquarePants]

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Description

Adds the ability to insert an IImageProvider or factory into the provider collection. This reduces boilerplate code when adding multiple providers.

[codecov]

Codecov Report

Merging #247 (198e8f4) into main (8892d76) will increase coverage by 0%.
The diff coverage is 100%.

@@         Coverage Diff         @@
##           main   #247   +/-   ##
===================================
  Coverage    84%    84%           
===================================
  Files        75     75           
  Lines      2036   2045    +9     
  Branches    294    296    +2     
===================================
+ Hits       1722   1733   +11     
+ Misses      230    228    -2     
  Partials     84     84           

Flag	Coverage Δ
unittests	84% <100%> (+<1%)	⬆️

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Impacted Files	Coverage Δ
...DependencyInjection/ImageSharpBuilderExtensions.cs	97% <100%> (+<1%)	⬆️
.../Synchronization/RefCountedConcurrentDictionary.cs	76% <0%> (+4%)	⬆️

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[ronaldbarendse]

Looks good, but the lifetime check can probably be skipped (same for removing), because clearing the providers/processors uses Services.RemoveAll() that only looks at the service type anyway.

[JimBobSquarePants]

@ronaldbarendse Agreed. Removed that additional check.

[ronaldbarendse]

I had another look at this and there are some issues with the current implementation:

builder.ClearProviders();
builder.AddProvider<PhysicalFileSystemProvider>();
builder.AddProvider<MockImageProvider>();
builder.InsertProvider<MockImageProvider>(2); // Does not throw ArgumentOutOfRangeException, because it's inserted after the existing 2 providers, but TryAddEnumerable only adds the first implementation

builder.ClearProviders();
builder.AddProvider<PhysicalFileSystemProvider>();
builder.InsertProvider<MockImageProvider>(0);
builder.InsertProvider<MockImageProvider>(1); // Does not change the index to 1 (last), because there's already an implementation added before it

See the implementation of TryAddEnumerable.