Bug 1711538 - Improve 'compatible_type()' r=lsalzman
Bug 1711538 - Improve 'compatible_type()' r=lsalzman

This renames compatible_type() to can_implicitly_convert_to()
which is a better name. The parameters are renamed to make
it more obvious what's going on. A note is added about
glsl misparsing of float literals and finally, implicit conversion of
float/double to int is removed because that's not supported by glsl.

Differential Revision: https://phabricator.services.mozilla.com/D115247

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/8ab369b87f17762ffeb856cb52735929c509e15c

servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender