googlefs: De-Googlize, rename to WebSearchFS

DuckDuckGo terms of use say "don't use our name for your app", so go for
a generic "Web Search". Mention them in the README, however.

Their terms of use say "don't remove our branding", but the results from
the HTML page have pretty much no branding. There's a logo at the top of
the page, but the terms of use also say "don't use our logo". So I guess
we're fine here.

Change-Id: Ib24a95faf4e727769ae00c1cb74fab79abde0379
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5498
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>