fix (RMS): REA iterate over a copy of the requests

[chaen]

We have had this stack trace the other day in the REA logs:

2026-05-28T15:09:04,088784Z RequestManagement/RequestExecutingAgent ERROR: Failed to execute finalize for Agent: RequestManagement/RequestExecutingAgent
Traceback (most recent call last):
  File "DIRAC/Core/Base/AgentReactor.py", line 129, in __finalize
    self.__agentModules[agentName]["instanceObj"].finalize()
  File "DIRAC/RequestManagementSystem/Agent/RequestExecutingAgent.py", line 433, in finalize
    self.putAllRequests()
  File "DIRAC/RequestManagementSystem/Agent/RequestExecutingAgent.py", line 195, in putAllRequests
    for requestID in self.__requestCache.keys():
RuntimeError: dictionary changed size during iteration

BEGINRELEASENOTES

*RMS

FIX:REA iterate over a copy of the keys

ENDRELEASENOTES

[fstagni]

Please rebase to get rid of the rtd error.