Don't assume support for VK_KHR_get_memory_requirements2,
enable the extension, if supported, during device creation.

Bug: angleproject:4830
Change-Id: I0faf955aac8a2ae4dea636f349225672e6717662
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2319079Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>