[TC Client] Add a way to generically handle request for the default process data

[ad3154]

Is your feature request related to a problem? Please describe.
This is related to a discussion in the discord.

Basically, if a user wants to specify a default time interval for a given process data variable, we currently don't expose a way to set one, so if a TC server doesn't command a specific time interval, the client is just out of luck.

Describe the solution you'd like
We should have some callback of some kind where, when the default process data is requested, we loop through the DDOP to find objects that are part of the default process data set, and for each one, allow the user to enable any triggers they want or mark them as needing to have their initial value sent, or both.

Describe alternatives you've considered
There's probably a few different ways to implement this... a callback like the request_value_command_callback , or maybe some pure virtual interface that needs to be passed into the object. Lot of options. Callback might be the most consistent with how we're doing other things at the moment.

Another option would be to have the users pass in all the possible data when constructing the DDOP, but that seems less desirable, because if we accept a binary DDOP, there'd still be no way to set it.

Additional context
Discord context