Vulkan: Remove ring buffer allocators * Removed the ring buffer allocator functionality from ANGLE: angle::RingBufferAllocator * Also removed the related common files. * (Pool allocators will be used at all times.) * Removed the placeholder functions from the pool allocator. * Removed the following BUILD flag: angle_enable_vulkan_shared_ring_buffer_cmd_alloc * Removed redundant line from ContextVk. Bug: b/410036490 Change-Id: I368fb93a66ddfd192018b09f65004a32339abd5a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6442640 Reviewed-by: Igor Nazarov <i.nazarov@samsung.com> Commit-Queue: Amirali Abdolrashidi <abdolrashidi@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>