Fix CI

[deemp]

• [x] Use restore and save actions for syntax and pipeline files to save them asap. Usually, these files don't affect the workflows correctness. Caching these files early improves build times of subsequent workflows.
• [x] Force re-runs of Setup.hs. Currently, some necessary modules aren't generated (link).
• [x] Don't use --prefetch because workflows fail (link) - see https://github.com/commercialhaskell/stack/issues/5435
• [x] Enable --pedantic
• [x] Disable --fast

[deemp]

A Windows runner is weird when it comes to Setup.hs (link):

• The runner doesn't like a single quote ' right after the last command in bash -c. E.g. bash -c '... happy Par.y' because it thinks the file is Par.y'.
• The runner doesn't like that happy Par.y is the last command. So, I put true as the last command.
• The runner doesn't like multiline bash commands. So, I concatenated commands with ;.
• The code page set outside of stack build is unavailable inside Setup.hs. So, I set the code page manually via chcp 65001 inside Setup.hs.

Additionally, on the Windows runner, it's necessary to chcp.com 65001 before running stack build --test that outputs Unicode characters.

See this comment about code pages.