HPCC-11637 Avoid multiple concourrent ECLWatch onActivity queries

Add a critical section block to allow only one thread to build
onActivity response; move the code of setting Activity response
into one function which is called after all of the response
information are collected; store the information (and information
collect time) into one WsSMC data member; reuse the information
if another Activity request comes through shortly after a recent
request.

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>
minor: I would code this as

activityInfoCache.setown(createActivityInfo(...))

to remove reference to the cache variable in the create function, and allow create to be called without caching.