test: support flexibly setting custom task options

Add a single TEST_ENTRY_CUSTOM hook that can be used to override task
entry defaults. Different tests can have different timeouts depending on
what is appropriate for each test. A separate TEST_OUTPUT_ENTRY hook is
no longer necessary.

In order to support per-task timeouts, the timeout field has been moved
into the task_entry_t struct. The default (5000) is now set as part of
TEST_ENTRY.
test: set getaddrinfo_fail timeout to 10000

getaddrinfo_fail can sometimes take slightly longer than the default
timeout of 5000. Set its timeout to 10000 to compensate, but leave the
timeout of all other tests at the default.