DM-54632: Eliminated obsolete code

[iagaponenko]

There are three commits in this PR:

• Remove queryDistributionTestVer from modules czar and cconfig

  • The code represents an experimental attempt to speed up query dispatch based on feedback from workers. The eliminated code was never finished, nor did it mature into any working prototype.
  • Another problem with the removed code was that it was making the package qana directly dependent on the Qserv frontend module czar. This was not right from the dependency management standpoint.

• Remove QuerySession.h:  int _isFinal

  This member has no actual effect on the query processing

• Remove unnecessary mutex locking from:

    // make new UserQuery
    // this is atomic
    ccontrol::UserQuery::Ptr uq;
    {
        lock_guard<mutex> lock(_mutex);
        uq = _uqFactory->newUserQuery(query, defaultDb, getQdispSharedResources(), userQueryId, msgTableName,
                                      resultDb);
    }
  

  The current query creation code is thread-safe after migrating the CSS database connector to the thread-safe implementation.

A few notes:

• The lock is known not to affect the performance of the mysql-proxy frontend due to another lock within the proxy that serializes query submission.
• The lock removal improves the performance of the http frontend since it doesn’t have any additional locks
• The ANTL4-based query parser is still the major factor that serializes query submission for the large query texts in both frontends.

[jgates108]

LGTM