Change MockCapsuleContainer to mock capsule with another capsule

[GregoryConrad]

trafficstars

signature like mock<T>(Capsule<T> capsule, Capsule<T> replacement)

Should hopefully fix the type issues experienced with the old setup & Dart’s type system, and will also be a much cleaner implementation, while providing more functionality. All around win.

[GregoryConrad]

mock-capsules.patch

Can start with this later. Will want to check the commit that added in the MockCapsuleContainer to see if this effectively reverts the (now) unwanted changes that one introduced.

[GregoryConrad]

https://github.com/GregoryConrad/rearch-dart/commit/fb3bc3c869f5ca245a7494f0dbbfc7983cbc55f7#diff-8866b9fadc5fe91154554f356b4cdcf54047cc6041a8e09a2475869ebbc388a6R156

So the above patch file properly reverts the CapsuleManager changes.