x11-toolkits/vte3: update to 0.78.2

Grab commits from upstream to fix a build issue as our libc++ does
not support formatting floats with std::from_chars and a radix
argument.

Incorporates a suggestion by Ivan Rozhuk to remove a flood of bogus
warnings.

Still broken on armv7 unfortunately.

While here, add missing dependencies and fix meson handling in
OPTIONS, as gtk4 became default enabled upstream.

PR: 275778
Co-authored-by: vishwin (gnome)