Cleanup AthSequencer, i.e. remove the obsolete FPE handling code (we
are using FPEAuditor instead). Also remove the "Atomic" property which
does not have any effect. Enable thread-checker.

Enable the thread-checker and replace the `std` random number
generation (which is not necessarily thread-safe) with `AthRNGSvc`.

Enable the thread-checker for the entire package. The explicit selection
of services to be checked is no longer needed and the relevant
thread-checker attributes have been removed again.

Disable thread-checker for:
- AthenaEventLoopMgr
- MixingEventSelector
- PyAthenaEventLoopMgr
- some of the testing code

Mark PageAccessControlSvc constructor as non-thread-safe.

Make the code pass the thread-checker. For this it was necessary to
explicitly pass the socket name (empty string as default like before) to
the relevant yampl functions.

Add thread-checker annotations where needed. CoreDumpSvc is of course
mostly not-thread-safe (and does not need to be).

Remove the sequence merge semantics workaround as the problem does not
seem to be reproducible anymore.

Gaudi v36r4 automatically handles the merge semantics of sets correctly.
The "Load" property is of type `DataObjIDColl`, which is an
`unordered_set` and thus we no longer need to define our own merge
semantics for it.

Explicitly qualify virtual methods called from ctors.

Suppress a couple cppcheck warnings.

Explicitly qualify virtual methods called from ctors.

This reverts merge request !46194

Prefer preincrement to postincrement for iterator classes.
Fix algtool argument order.

Introduced AthenaMPConfig.py script with the CA-based configuration for AthenaMP.
Also introduced a bunch of MP-specific configuration flags, and a new flag
for setting MaxFilesOpen property of PoolSvc, which needs to be modified
when AthenaMP runs with the Shared Reader

Enable thread-safety checking and fix warnings.

gcc12 warns about comparing this to nullptr, since this being null
is undefined behavior.

Just remove the check.  If this is null we'll anyway crash on the next line.

For it to work correctly, AddressRemappingSvc must be last on
ProxyProviderSvc's list of providers.  Add code in ProxyProviderSvc
to enforce this.

cf ATR-24754

Make the `StoreGateSvc::keys` method `const`.