Remove cotire, rewrite #include's and fix all compile errors which appeared after cotire removal

[leha-bot]

This PR drops cotire and broken PCH, and rearrange headers to avoid cycles which has been hidden by PCH.

Also this PR closes #133

CAUTION: Merge only if:

• This build compiles on MacOS;
• This build compiles on Windows;
• This build compiles on Linux;
• This build compiles on CI;
• All style quirks which I accidently may add to codebase are reviewed and fixed;
• The commits contain only relevant changes (it's not at the PR creation moment!);

~~~Split huge commits by @leha-bot and @crackedmind;~~~
~~~Merge parts with related @berkus commits;~~~
~~~Ensure that the commit history is clear to understand.~~~

UPD: We decide to squash them all (instead of completing subtasks).

[crackedmind]

✅ Build kepka 1.0.126-ekebaqjc completed (commit 52d5b47487 by @leha-bot)

[crackedmind]

✅ Build kepka 1.0.126-pgksfebp completed (commit f224faa6ee by @leha-bot)

[crackedmind]

✅ Build kepka 1.0.126-kpghrbvr completed (commit 499538ebec by @leha-bot)

[crackedmind]

✅ Build kepka 1.0.126-bwgcxxao completed (commit f3f43c9351 by @berkus)

[berkus]

This is good to go, but i'd rearrange/squash several commits before merging.

[leha-bot]

TODO: cherry-pick one line related to core include paths from my commit and squash with this commit

[leha-bot]

This string must be squashed into a8e998a

[leha-bot]

TODO: move out timer-related utils from utils to timer to avoid include bloating

[crackedmind]

✅ Build kepka 1.0.129-oqbhvnun completed (commit 08a7294d3a by @)