Fixes validation error when calling render_buffer_init_exportable
VUID-vkBindBufferMemory-memory-02726(ERROR / SPEC): msgNum: -168767885 - Validation Error: [ VUID-vkBindBufferMemory-memory-02726 ] Object 0: handle = 0xe88693000000000c, type = VK_OBJECT_TYPE_BUFFER; Object 1: handle = 0xcad092000000000d, type = VK_OBJECT_TYPE_DEVICE_MEMORY; | MessageID = 0xf5f0ce73 | vkBindBufferMemory(): The VkDeviceMemory (VkDeviceMemory 0xcad092000000000d[]) has an external handleType of VK_EXTERNAL_MEMORY_HANDLE_TYPE_OPAQUE_FD_BIT which does not include at least one handle from VkBuffer (VkBuffer 0xe88693000000000c[]) handleType Unhandled VkExternalMemoryHandleTypeFlagBits. The Vulkan spec states: If the value of VkExportMemoryAllocateInfo::handleTypes used to allocate memory is not 0, it must include at least one of the handles set in VkExternalMemoryBufferCreateInfo::handleTypes when buffer was created (https://www.khronos.org/registry/vulkan/specs/1.3-extensions/html/vkspec.html#VUID-vkBindBufferMemory-memory-02726)
Objects: 2
[0] 0xe88693000000000c, type: 9, name: NULL
[1] 0xcad092000000000d, type: 8, name: NULL
Some downstream user might want to use the very handy comp_buffer_init()
helper to create buffers, but the latter does not cover the case when
the buffer needs to be exportable for API interoperability.
Add a new comp_buffer_init_exportable() helper to cover that case, this
is done in a way that is not particularly invasive for existing users of
comp_buffer_init(), as all the logic about the exportability is handled
by the new function.
The size field in comp_buffer was never assigned, and also never used as
all comp_buffer users rely on the allocation_size field.
Use the size field to store the size originally requested when creating
the buffer which could be different from the value returned in the
allocation_size field.
Having both sizes available allows a user to check if allocation_size is
in fact different from the requested size.
This matches the OpenXR usage: the array is the plural of the element type,
and the count is the singular element type plus "count" (usually CountOutput
because of the two-call idiom)
Includes fixes to other code to match API changes.
