Make conflict_analysis class no longer be friend of cdcl_sat

[codecov[bot]]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (f25b234) 96.31% compared to head (a50b544) 96.24%.

Files	Patch %	Lines
include/solver/cdcl_sat_impl.hpp	88.23%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #34 +/- ## ========================================== - Coverage 96.31% 96.24% -0.07% ========================================== Files 25 25 Lines 1572 1596 +24 Branches 1144 1155 +11 ========================================== + Hits 1514 1536 +22 + Misses 11 10 -1 - Partials 47 50 +3 ``` | [Flag](https://app.codecov.io/gh/michael-veksler/solver/pull/34/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Michael+Veksler) | Coverage Δ | | |---|---|---| | [Linux](https://app.codecov.io/gh/michael-veksler/solver/pull/34/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Michael+Veksler) | `61.29% <68.88%> (+0.19%)` | :arrow_up: | | [Windows](https://app.codecov.io/gh/michael-veksler/solver/pull/34/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Michael+Veksler) | `99.21% <95.83%> (-0.14%)` | :arrow_down: | | [macOS](https://app.codecov.io/gh/michael-veksler/solver/pull/34/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Michael+Veksler) | `35.37% <11.11%> (-0.32%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Michael+Veksler#carryforward-flags-in-the-pull-request-comment) to find out more.

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