repoview: make propertycache.setcache compatible with repoview Propertycache used standard attribute assignment. In the repoview case, this assignment was forwarded to the unfiltered repo. This result in: (1) unfiltered repo got a potentially wrong cache value, (2) repoview never reused the cached value. This patch replaces the standard attribute assignment by an assignment to `objc.__dict__` which will bypass the `repoview.__setattr__`. This will not affects other `propertycache` users and it is actually closer to the semantic we need. The interaction of `propertycache` and `repoview` are now tested in a python test file.

Testing that hghave does not crash when checking features

  $ "$TESTDIR/hghave" --test-features 2>/dev/null