Future proofing: Rewrite remaining `implicit`s to Scala 3 replacements

[MateuszKowalewski]

• [x] Get rid of implicitly
• [ ] Figure out what to do about the implicit classes

[TomasMikula]

I have removed a bunch of unnecessary syntactic extensions from CoreLib (i.e. ones that have a straightforward alternative): https://github.com/TomasMikula/libretto/commit/3c5460b0330aa5a5533bdc3f43b27366006c7ec5#diff-0c2a475aa7b1c448e7cdd4bec8598255acb742ea83f9aa91f7eb872473aca154L1604-L1871

Still need to write tests for the remaining ones.

[MateuszKowalewski]

Do I get this right, now the language is smaller, but more composable?

Something like that is good for learning. Nice move!

[TomasMikula]

The core language is the same. I just eliminated some extra sugar and the syntax is more regular.

[TomasMikula]

Got rid of implicitly.