IsEnterprise currently returns `true` when `IsTenancy` returns true. We
prefer that this behavior is orthogonal. This commit adds failing tests to
the instances where IsEnterprise should not behave the same as IsTenancy.
These test cases are expected to pass with the inclusion of the coming
improvements to go-gh to handle the orthogonality of IsEnterprise and
IsTenancy.
The github.com API right now doesn't seem to make merge queue APIs
available to people who use PAT to authenticate gh requests. This
switches the conditional request strategy to also do feature-detection
for dotcom (instead of just for Enterprise).
