TimingModel validation based on TOAs

[abhisrkckl]

There are checks we can do to ensure that the user is not accidentally using the wrong par/tim combination, like START, FINISH, NTOAS, DMDATA, etc.

We can also validate some of the TimingModel components based on the given TOAs object:

1. DMJump should not be used with narrowband TOAs
2. PLDMNoise does not work properly with wideband TOAs
3. If any of the TOAs have a terrestrial observatory, an Astrometry component should be present,
   etc...

We can emit warnings for such things from the get_model_and_toas() function or the constructor of the Residuals class.

See also discussion in #1731.