Fix ClockTest on Windows

[traversaro]

Without these changes, the ClockTest is not passing on Windows, the changes are:

• Go back to run the simulation just for ~10 iterations (i.e. 10 ms), and compute correctly the expected nanoseconds published on the clock (without doing iterations-1 that was what was causing the test to fail on Windows). Furthermore, do not use 1e6 seconds as tolerance for seconds, but just expect them to be equal.
• Add Finalize() call to the fixture, otherwise there was a "[Wrn] [D:\bld\gz-sim8_1713968558858\work\src\TestFixture.cc:208] Fixture has not been finalized, any functions you attemptedto hook into will not be run. It is recommended to call Finalize()before accessing the server." warning

[xela-95]

Rebased and squashed.

[xela-95]

Merging 🚀