User facing messages/warnings/errors should be localized, and documented

[radical]

Prompted by #78755 (comment)

The shipping tasks in src/tasks have user facing strings in the form of:

• messages (Log.LogMessage - especially the Normal, and High importance ones)
• warnings
• errors

These need to be identified, and localized.

Questions:

• Do all 3 need that treatment?
• Are there any existing cases where such messages are localized that can be used as examples to do this?
• Do the user-facing Errors need to be assigned codes too?
• Where, and how should the Errors, and Warnings be documented?

cc @akoeplinger @maraf @lewing @steveisok

[ilonatommy]

Questions:

• Do all 3 need that treatment?
• Are there any existing cases where such messages are localized that can be used as examples to do this?
• Do the user-facing Errors need to be assigned codes too?
• Where, and how should the Errors, and Warnings be documented?

My plan, please let me know if it can be improved:

• Errors and warnings should be localized. I am not sure about messages, it will depend on the amount of work connected with it.
• We are localizing a bunch of strings in libs, e.g.:
  https://github.com/dotnet/runtime/tree/1df411180b30546cf58426d18b1c86b704f0753a/src/libraries/Microsoft.CSharp/src/MultilingualResources
  https://github.com/dotnet/runtime/tree/1df411180b30546cf58426d18b1c86b704f0753a/src/libraries/System.Runtime.InteropServices/gen/Common/Resources/xlf
  but some of them e just keep in English version as resources, no translations:
  https://github.com/dotnet/runtime/blob/1df411180b30546cf58426d18b1c86b704f0753a/src/libraries/System.Private.CoreLib/src/Resources/Strings.resx
• Yes. E.g. users can suppress specific warnings using the codes. What's more, codes should be unique for a given string, so we can use them as keys for localization.
• Compilation errors are documented here and only them. Aspnetcore codes are documented in their repo here and this looks like a good pattern. To keep it simple, I would create same-named doc in the corresponding location in runtime repo: https://github.com/dotnet/runtime/tree/main/docs

[ilonatommy]

Connected issue: #85067