RESTXQ: %basex:lock

[ChristianGruen]

When %basex:lock is assigned to an updating RESTXQ endpoint, the corresponding function should only be invoked once in parallel:

declare
  %rest:path('/test')
  %base:lock('LOCK')
function local:sleep() {
  prof:sleep(10000)
};

Currently (or at least in BaseX 10.7), %basex:inline(0) needs to be added to enforce this behavior.