repoview: flag `server.view` as experimental
Ideally, the non-experimental version of `experimental.extra-filter-revs` will
cover the use case for `server.view=immutable` well enough than having to have
this dedicated configuration. Since `server.view` is not part of any release, I
would prefer to have it marked as experimental to avoid having it to support it
for ever.
local test passed
addgroupcopy test passed
clone test passed
lowlevelcopy test passed
slicing test passed
issnapshot test passed
findsnapshot test passed