Instead of doing a slow depth clear, we can do depth fast clear in
vkClearAttachments.

v2: (Nanley Chery)
- Clear stencil surface along with depth.
- Check for multilayer resources.
- Lookout for state.attachments.
- Fallback on slow clear for BDW and CHV if conditional rendering
  enabled.
- Keep flush in same function.

v3: (Nanley Chery)
- Return immediately after fast clearing.
- Remove unnecessary comment.

v4: (Nanley Chery)
- Add assertion for BLORP_BATCH_NO_EMIT_DEPTH_STENCIL.
- Remove unnecessary local variable.
- Add 3DSTATE_WM_HZ_OP comment.

v5: (Nanley Chery)
- Fix comments.
- Don't take fast depth clear path if BLORP_BATCH_PREDICATE_ENABLE set.
- Refactor code in can_hiz_clear_att.

Signed-off-by: Sagar Ghuge <sagar.ghuge@intel.com>