1. Cleanup boilerplate code
2. Change property declaration to new method
3. Change function names in AthMonitorCfgHelper
4. Add AOD to TestDefaults.py
5. Add override keyword to functions

- `HistogramDef`: fix a parsing bug where the histogram definition
  string had to end with a trailing comma for 1D histograms without
  labels and options.
- Remove the trailing comma produced by `defineHistogram`
- Adapt the existing C++ unit tests and add a test for `TProfile2D`
- Deprecate the use of "label1:label2" syntax in `defineHistogram`
- Add a unit test for the `defineHistogram` method
- Change line endings from DOS to UNIX in source files

Make some trivial code changes to make it possible to compile some of
the Monitored classes outside of athena:
- Rely on explicit StatusCode->bool conversion instead of calling
  isFailure()
- Add missing include files

In addition, remove `std` import and change line endings from DOS to
UNIX.

The number of events processed in the SimplePOSIXTimeKeeperSvc is unpredictable.
Adjust comparison to be insensitive to this.

Enabable thread-safety static checks; various cleanups.
Legacy DataHandle and associated functions marked as not thread-safe.

The default value for the `HistPath` property was by mistake changed in
commit 4a2edffa and broke the automatic booking of histograms under the
tool's parent's name. Revert the default value back to an empty string
and improve documentation.

Also some general cleanup of the code:
- remove irrelevant `virtual`
- remove declaration of `InterfaceID`
- remove import of `std` namespace as `std::` was used in most places
- spell and grammar check

Another step towards deprecating DataHandle: remove all methods to retrieve
the referenced object as non-const.

The thread-safety checker wasn't property checking class constructors.
Fix a few warnings that appear once that is corrected.

The AlgExecStateSvc is not functional before the first algorithm
execution. Accessing it will result in a `GaudiException` that needs to
be caught so that the crash handling can continue.

In C++11, implicit declarations of copy and assignment are deprecated if the
class has a user defined destructor or copy or assignment.  gcc9 now warns
about this by default.
Adjust to avoid the warning.

When finishing the trim() operation, the begin pointer must be updated
before queuing the dummy impl object for discard.  Otherwise, another thread
could potentially see a pointer to a deleted object.

Trying to fix infrequent crashes in CondCont_test observed in nightlies and CI.

Allow overriding the location of test files via an optional environment
variable.  Useful for builds on systems where cvmfs is not available.

Clang warnings: unused private data members.

Fix typo in include guard.

Test has been timing out frequently in recent nightlies.

Update for headers moved from SGTools to AthenaKernel.

Update for headers moved from SGTools to AthenaKernel.

Update for headers moved from SGTools to AthenaKernel.

Update for headers moved from SGTools to AthenaKernel.

Should no longer be used from anywhere.

In C++11, implicit declarations of copy and assignment are deprecated if the
class has a user defined destructor or copy or assignment.  gcc9 now warns
about this by default.
Adjust to avoid the warning.

- Move the reading of EventInfo weights to the only client
  AthFilterAlgorithm
- add a mutex to the addEvent method called by AthFilterAlgorithm