vkCmdExecuteCommands implementation

vkCmdExecuteCommands implementation

Basic support for executing secondary command buffers, without
support for any inheritance features.

Bug b/118619338

Change-Id: Ie3453018a45a722ecfa4f1acd20c95442fbb3d9b
Tests: dEQP-VK.memory.pipeline_barrier.host_write_transfer_src.*
Tests: dEQP-VK.api.command_buffers.allocate_single_secondary
Tests: dEQP-VK.api.command_buffers.allocate_many_secondary
Tests: dEQP-VK.api.command_buffers.trim_command_pool_secondary
Tests: dEQP-VK.api.command_buffers.record_single_secondary
Tests: dEQP-VK.api.command_buffers.record_many_secondary
Tests: dEQP-VK.api.command_buffers.submit_twice_secondary
Tests: dEQP-VK.api.command_buffers.record_one_time_submit_secondary
Tests: dEQP-VK.api.command_buffers.secondary_execute
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27493
Tested-by: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>