Update user agent strings and make them static
Update user agent strings and make them static

Only three recognized agent keywords are supported and replaced with
the corresponding user agent string: "CHROME", "FIREFOX", and "SAFARI".
Other user agents are passed as received.

It is no longer possible to add version to the recognized keyword. E.g.,
"CHROME 81.0.132.5" has the same effect as "CHROME".

Issue: tiliado/nuvolaruntime#575

tiliado/nuvolaruntime,tiliado/nuvolaruntime,tiliado/nuvolaruntime,tiliado/nuvolaruntime