Clippy and refactor

[lrvideckis]

also install oj-verify tool later in CI (right before running lib checker tests) so we don't have to wait for it to install to see the results of all the cargo checks

[lrvideckis]

I learned that since we have a single crate, on any commit, the entire crate is rebuild, so oj-verify tool thinks everything changed, and then reruns all tests

so we can either split up the lib to be one crate for each file (Pro: the only tests that will be rerun are for changed files in that commit), but I don't really want to do this

What I think we should do: just keep it as is, and have CI rerun every test on each commit. Con: we'll have to wait longer for CI. But we can always run individual tests locally and know the result faster;

Pro: we can completely remove the .verify-helper/timestamps.remote.json file (every test is rerun anyways, so no need to save this file); This file was pretty annoying to deal with (it caused merge conflicts)

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other changes in this PR:

• running jobs in parallel: --jobs 4: github CI runs with 4 cores
• 1 hour timeout: --timeout 3600 which should force CI to run for an hour; which hopefully will be enough time to run all tests
• split up CI into 2 jobs: one with all cargo ... stuff, and the other job which only runs the library checker tests (this second job will take forever, so let's start it right away)
• fixed clippy warnings