Previously, separate interfaces were defined for Reserve and Unreserve
plugins. However, in nearly all cases, a plugin that allocates a
resource using Reserve will likely want to register itself for Unreserve
as well in order to free the allocated resource at the end of a failed
scheduling/binding cycle. Having separate plugins for Reserve and
Unreserve also adds unnecessary config toil. To that end, this patch
aims to merge the two plugins into a single interface called a
ReservePlugin that requires implementing both the Reserve and Unreserve
methods.
Under the feature gate DefaultPodTopologySpread, which will disable the legacy DefaultPodTopologySpread plugin from the default algorithm providers.
Signed-off-by: Aldo Culquicondor <acondor@google.com>
