search plugin: do not crash on missing lang options, inform instead

[ultrabug]

• fallback to english on missing search.lang option
• support search.lang territory pt_BR -> pt

[ultrabug]

This replaces #2564 to address your points #2535 (comment) with #2535 (comment)

Example output:

INFO     -  Option search.lang 'pt_BR' fallbacked to 'pt'
INFO     -  Option search.lang 'zz_BR' is not supported, falling back to 'en'

[oprypin]

Thanks! The approach looks good to me. Let's get this done :)

CI is failing, though 😬

[ultrabug]

Fixing tests now, should be good soon

[ultrabug]

Good for me now 👍

[ultrabug]

Thanks for the review @oprypin

[oprypin]

Ah thanks for the great fix.

@ultrabug so you probably saw that I mentioned that a release is coming on Sunday [today]
but it seems like there's still some language PRs that we could merge now. So let's not rush with the release.

[ultrabug]

Yes mate indeed, I'll check the pt_BR PR out later today, thanks