ResourceUseList::add is called repeatedly when we need to
track a resource's usage in a context. Instead of a
potential memory operation on each add we reserve memory
upfront for about 4k SharedResourceUse objects. If the
vector grows larger, it will be automatically handled by
std::vector's allocator.

Bug: angleproject:4950
Change-Id: Ic85ed44a6662819621ee9a47f43dd2542b73114d
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2375801Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>