chore: maintenance, CI and misc improvements

[cyyynthia]

• Upgraded all dependencies to latest versions, fixing all possible npm audit complaints of vulnerable versions
• Ditched form-data; Node 18+ has support for FormData natively
• Migrated to ESLint v9 config format
• Made scripts TypeScript instead of plain js
• Simplified TS configuration to use presets from tsbases
• Moved tests out of src - TS config tweaks no longer mess with the output
• Added #cli and #tests imports specifiers to cleanup some ../../../../ hell
• Updated TM grammars; they are also now minified to take less space
• Upgraded CI action versions to v4
• Made unit tests and e2e tests run on Linux, Windows, and MacOS on Node 18, 20 and 22
• And some other misc tweaks 😅

Additionally, the (currently-broken) code reliant on ts-node has been commented out; a more stable solution appears to be based on what other packages do to compile the ts file to a temporary .js file and use this js file instead.

[cyyynthia]

I was quite eager to get the CI up and running on Windows and Mac but it seems that GitHub Actions support for it is... not great, to say the least. :(

The complete lack of proper Docker support makes it very difficult to get a test instance of Tolgee running... :/

• On macOS, it requires some workarounds that don't seem to always behave nicely, and don't work on M1 and M2 powered macs
• On Windows, their setup predates WSL2 and as such while Docker is installed, it doesn't run in Linux mode via WSL2 - so it can't run the Tolgee image