summary: separate checking incoming/outgoing and showing remote summary
This patch separates checking incoming/outgoing and showing remote
summary, as a preparation for refactoring in succeeding patches,
because:
- checking incoming/outgoing may be needed, even if "--remote" is
not specified for "hg summary"
- checking incoming/outgoing may not be needed simultaneously
"hg summary --large" without "--remote" is typical case for these.