gallium,util: Pull u_indices and u_primconvert back into gallium

gallium,util: Pull u_indices and u_primconvert back into gallium

This was moved in !13741 but doing so created a link-time dependency
between util and gallium which causes problems for Vulkan drivers.
Meanwhile, having mesa/main depend on gallium is fine now that we don't
have any classic drivers.  It's a bit circular but should be harmless.

Fixes: 97ba2f2fd486 ("move util/indices to core util")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/8098
Acked-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20734>
(cherry picked from commit d292cb82b8ef1311eb4b78af2c90b1840ba5a6bf)