venus: add support for VK_KHR_dynamic_rendering

Corresponding virglrenderer change: virgl/virglrenderer!859 (merged)

Tested in linux ChromeOS VM with host ANV:

dEQP-VK.dynamic_rendering.*
---------------------------
BEFORE
Test run totals:
  Passed:        0/3967 (0.0%)
  Failed:        0/3967 (0.0%)
  Not supported: 3967/3967 (100.0%)
  Warnings:      0/3967 (0.0%)
  Waived:        0/3967 (0.0%)

NOW
Test run totals:
  Passed:        3363/3967 (84.8%)
  Failed:        0/3967 (0.0%)
  Not supported: 604/3967 (15.2%)
  Warnings:      0/3967 (0.0%)
  Waived:        0/3967 (0.0%)


dEQP-VK.draw.renderpass.*
-------------------------
BEFORE
Test run totals:
  Passed:        973/6764 (14.4%)
  Failed:        12/6764 (0.2%)
  Not supported: 5779/6764 (85.4%)
  Warnings:      0/6764 (0.0%)
  Waived:        0/6764 (0.0%)

NOW
Test run totals:
  Passed:        973/6764 (14.4%)
  Failed:        12/6764 (0.2%)
  Not supported: 5779/6764 (85.4%)
  Warnings:      0/6764 (0.0%)
  Waived:        0/6764 (0.0%)

dEQP-VK.draw.dynamic_rendering.*
--------------------------------
BEFORE
Test run totals:
  Passed:        0/8499 (0.0%)
  Failed:        0/8499 (0.0%)
  Not supported: 8499/8499 (100.0%)
  Warnings:      0/8499 (0.0%)
  Waived:        0/8499 (0.0%)

NOW
Test run totals:
  Passed:        1597/8499 (18.8%)
  Failed:        23/8499 (0.3%)
  Not supported: 6879/8499 (80.9%)
  Warnings:      0/8499 (0.0%)
  Waived:        0/8499 (0.0%)

The Not supported in dEQP-VK.draw.* are from lack of VK_EXT_multi_draw support in Venus.
Failures in dEQP-VK.draw.* are from dEQP-VK.draw.{renderpass,dynamic_rendering}.linear_interpolation.*

/cc @zzyiwei