Api: Forbid binding to subcomponets directly, tweak component factories.

[Jeffset]

Before the patch, if a child component didn't have a builder its instance could be injected directly. Such behavior is confusing and vanilla dagger doesn't support that.

The reasons of why this behavior was here in the first place are historical and date back to the time when yatagan didn't support child components factory methods, and relied solely on Module.subcomponents.

This patch removes the confusing behavior and makes it as in vanilla dagger.

Also, now every method in a component interface returning a non-root component is considered a component-factory. Before the patch only the methods with arguments were considered a factory. However, this imposes new restrictions on how component instances can be exposed from component interfaces, as such usages will now be considered as factories, not entry-points. This leads to some tweaks in tests. But such cases seem of little use in the real world scenarios. And, anyway, that's still how vanilla dagger works.

This is a breaking change, but it's okay for 2.0.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 85.71429% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 83.37%. Comparing base (e8d3224) to head (d6bf9d2).

Files	Patch %	Lines
.../yatagan/codegen/impl/ComponentFactoryGenerator.kt	75.00%	0 Missing and 1 partial :warning:
.../yandex/yatagan/codegen/impl/ComponentGenerator.kt	66.66%	0 Missing and 1 partial :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #154      +/-   ##
============================================
- Coverage     83.71%   83.37%   -0.35%     
+ Complexity     1555     1538      -17     
============================================
  Files           191      190       -1     
  Lines          7548     7523      -25     
  Branches       1416     1412       -4     
============================================
- Hits           6319     6272      -47     
- Misses          727      746      +19     
- Partials        502      505       +3     

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