Vulkan: Avoid buffer overflow by ignoring duplicate extensions

For any instance extension that a Vulkan driver supports, if a
VkInstance is created with that extension listed multiple times, the
2nd-nth times should be ignored.  That avoids overwriting an array in
CreateInfoWrapper::FilterExtension().

Test: Manual testing with logcat
Bug: 288929054
Change-Id: I096a6752e0f4abef868efdb6f8b4bcbd0c0c79cd