Previous code relied on GLSL parameter order (something that's always
ill-formed on an IR design). This approach passes spatial coordiantes
through operation nodes and array and depth compare values in the the
texture metadata. It still contains an "extra" vector containing generic
nodes for bias and component index (for example) which is still a bit
ill-formed but it should be better than the previous approach.

Co-Authored-By: ReinUsesLisp <reinuseslisp@airmail.cc>

Co-Authored-By: ReinUsesLisp <reinuseslisp@airmail.cc>

Co-Authored-By: ReinUsesLisp <reinuseslisp@airmail.cc>

i965 (and probably all mesa drivers) require GL_PROGRAM_SEPARABLE when using
glProgramBinary. This is probably required by the standard but it's ignored by
permisive proprietary drivers.

Converts many of the Find* functions to return a std::optional<T> as
opposed to returning the raw return values directly. This allows
removing a few assertions and handles error cases like the service
itself does.

This member function doesn't actually modify instance state, so it can
be marked as a const member function.

This was missed within #2075. Renames the member function to make it
consistent with the rest of the Find* functions.