Log viewer: make log_dir query parameter optional

[tadamcz]

• Make log_dir query param optional
• Add simpleHttpSingleFileApi, to be used if only log_file is passed

Previous behaviour

Throws an error if only log_file is passed:

Uncaught TypeError: Cannot read properties of null (reading 'replace')
    at simpleHttpApi (api-http.mjs:17:36)
    at resolveApi (index.mjs:39:19)
    at index.mjs:49:16

New behaviour

Uses the new simpleHttpSingleFileApi when only log_file is passed.

[dragonstyle]

Thank you for this PR!

I've made changes that make log_dir optional a slightly different way in #1189 . In general, we would to handle conditional treatment of files by type using the higher level client-api. If after testing you agree that PR does what you need, I'd suggest we can close this PR in favor of that one.

[tadamcz]

Sounds good! I expect that your PR does what I need, but can report back once I have definitively confirmed that by testing (might be on Monday though).

[tadamcz]

Responded on #1189

[tadamcz]

Closing in favour of #1189