freedreno/ir3: convert over to ralloc

The `ir3_shader` is the root mem ctx, with `ir3_shader_variant` hanging
off that, and various variant specific allocations hanging off the
variant.

This lets us delete a bunch of cleanup code.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5508>
3 files changed