HPCC-11958 Add Roxie State check to preflight

The similar logic in ecl-roxie is used by this fix to
retrieve and format information about roxie state (hash).
The information is displayed inside ECLwatch preflight
page (a new column 'Roxie State'). WsMachine thread pool
is used to improve the performance of retrieving the
information.

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>
Looks like maybe context is no longer used, and can be removed from this class?  We should be very careful to make sure anything we do on a context in a different thread is thread safe.  It was designed to be associated with the main thread of a transaction and may need to be made threadsafe when and where needed.