HPCC-9523 - Fix potential hashdedup deadlock

If rehashing allocates, can cause memory callback to spill the
hash table involved and deadlock.
Be careful when allocating in a mutex.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
unit tests

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
step1

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
HPCC-9252 Allow a different locking primative to reduce contention

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Updates to the newspin class - still not a great alternative

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Various more experimental changes

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>