aco: Combine v_cvt_u32_f32 with insert to v_cvt_pk_u8_f32.

aco: Combine v_cvt_u32_f32 with insert to v_cvt_pk_u8_f32.

No Foz-DB difference on Navi21.

Foz-DB GFX11:
Totals from 746 (0.55% of 134913) affected shaders:
CodeSize: 8430248 -> 8416128 (-0.17%); split: -0.17%, +0.00%
Instrs: 1617202 -> 1614707 (-0.15%)
Latency: 13943398 -> 13934161 (-0.07%); split: -0.07%, +0.00%
InvThroughput: 2601620 -> 2596624 (-0.19%); split: -0.20%, +0.01%
Copies: 114346 -> 114334 (-0.01%); split: -0.01%, +0.00%
PreVGPRs: 48314 -> 48312 (-0.00%)

Signed-off-by: Georg Lehmann <dadschoorse@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18492>