Check CLI text translation state and consider enabling translations when headless

[pljones]

What is the current behaviour and why should it be changed?

The client and server code behave differently on start up when headless, in regards to loading translations.

Ideally both would load translations once the application instance had been created and all text displayed - either in the GUI or to the console - would be translatable.

Describe possible approaches

• Review existing code to identify any text that should be translated that is not.
• Review existing code to identify any text that should not be translated that is.
• Raise a PR to resolve the above.
• Once that's done, review the start up code in src/main.cpp to ensure translations are loaded as soon as the run time language has been established. Currently, this must be after command line and settings processing as both can affect the language selection.

Has this feature been discussed and generally agreed?

Mentioned, possibly several times, previously. Most recently in #3139.