- Use a custom descriptor structure for everything, so we have control
  over alignment
- Fix descriptor pool size to include the proper number of headers
- Remove a level of indirection in buffer descriptor handling
- Correctly handle VK_WHOLE_SIZE for buffer bound ranges
- Handle robustness + dynamic offset interaction where the dynamic
offset places the bound range partially outside the buffer.
- Sanity checks from Ben's original 'seatbelts' patch

Bug: b/123244275
Test: dEQP-VK.binding_model.*
Change-Id: I18cc40805aac7256a7d57a21af003f21f630b2e6
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/30168
Presubmit-Ready: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Chris Forbes <chrisforbes@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>