Performance optimizations (#21)

* simplify Task extension method

* .ConfigureAwait(false) all the things

* Performance optimizations; make Eff instances fully referentially transparent.

* include debug testing in dockerfile

* fix builder issues

* rearrange methods

* add more comments

* fix linux build error

* mark delayed state machine as readonly

* method ordering

* Replace Eff type hierarchy with EffEvaluator

* unify EffAwaiter with EffStateMachine

* Ensure IEffStateMachine.GetAsyncStateMachine() returns copied replicas

* add missing fix

* simplify sample code

* add coverlet

* sample code cleanups

fix bug in aspnetcore sample

Add more unit tests; further refactorings (#20)

* Move Eff.Effects applications to Eff project

* factor EffExecutor into an IEffectExecutor method

* refactor and extend unit test coverage

* exception handler should return Task<TResult>

* rename EffAwaiterBase to Awaiter

* add cancellation effect tests

* add tests for throwing awaiter handlers

* deprecate eff type handlers and inline into executor method

* use lazy reflection calculations in state machine cloner

* refactor EffStateMachine.cs

* add dependency injection tests

* add nullable annotations everywhere

* add NonDeterminism tests and fix bugs

* update maybe sample

Refactor namespaces (#19)

* rename Nessos.Eff root namespace to Nessos.Effects

* refactor namespaces in Eff.Core

* refactor Eff.Effects and add cancellation effect

* move Eff project from Eff.Core folder

Simplify aspnetcore sample (#18)

* Simplify aspnetcore sample

* fix build

Simplify naming of awaiter classes (#17)

infra fixes

Update README.md