linker: Set block bindings based on UniformBlocks rather than UniformStorage

linker: Set block bindings based on UniformBlocks rather than UniformStorage

For blocks, gl_shader_program::UniformStorage isn't very useful.  The
names stored there are the names of the elements of the block, so
finding blocks with an instance name is hard.  There is also only one
entry in ::UniformStorage for each element of a block array, and that is
a deal breaker.

Using ::UniformBlocks is what _mesa_GetUniformBlockIndex does.  I
contemplated sharing code between set_block_binding and
_mesa_GetUniformBlockIndex, but building the stand-alone compiler and
the unit tests make this hard.  I plan to return to this effort shortly.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76323
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Cc: "10.1" <mesa-stable@lists.freedesktop.org>
Cc: github@socker.lepus.uberspace.de