fix: Make file upload work when waved run separately #2225

[marek-mihok]

The PR fulfills these requirements: (check all the apply)

• [x] It's submitted to the main branch.
• [x] When resolving a specific issue, it's referenced in the PR's title (e.g. feat: Add a button #xxx, where "xxx" is the issue number).
• [x] When resolving a specific issue, the PR description includes Closes #xxx, where "xxx" is the issue number.
• [ ] If changes were made to ui folder, unit tests (make test) still pass.
• [ ] New/updated tests are included

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This PR fixes the issue when H2O_WAVE_WAVED_DIR has a wrong value in some scenarios. The fix is accomplished by finding the PID of the waved/waved.exe and getting its CWD which is then set to H2O_WAVE_WAVED_DIR env variable.

Successfully tested on both Mac and Windows.

Closes #2225

[marek-mihok]

Can we do without external lib though?

@mturoci my research shows there is no pythonic (or other simple) way of getting process cwd by its name on Windows. Libs like psutil or win32com use complex solutions for this simple problem.

Maybe we could include psutil as the os specific dependency? For Windows only? And use external lib free solution otherwise?

[mturoci]

there is no pythonic (or other simple) way of getting process cwd by its name on Windows

In that case, you can either implement for UNIX systems only and defer to HTTP on err and Windows or go for HTTP everywhere and keep using H2O_WAVE_WAVED_DIR for speedup if needed.

[mturoci]

Edit: Let's just go for HTTP uploads when waved is run separately and local uploads when waved is started automatically. This would be the safest and simplest option.

[mturoci]

Added a small refactor. @marek-mihok please verify if works. If it does, good to merge. Thanks!

[marek-mihok]

@mturoci works, it's good to go.