Checkpointer module

Create a module for saving the simulation state and restarting it, which is particularly essential for long-running simulations.

ClimaCoupler.jl Checkpointer module: https://github.com/CliMA/ClimaCoupler.jl/blob/main/src/Checkpointer.jl
ClimaAtmos.jl callbacks: https://github.com/CliMA/ClimaAtmos.jl/blob/f751e691c05ae935ff30d82b7ef804021f5355ea/src/callbacks/callbacks.jl

ClimaCoupler.jl Checkpointer tests: https://github.com/CliMA/ClimaCoupler.jl/blob/main/test/checkpointer_tests.jl

tracked by #39

## To Do
- [ ] Copy all functions from both repos
- [ ] Copy all tests from both repos
- [ ] Generalize function interfaces, extend functionality for all users
- [ ] Update test usage, make sure tests pass
- [ ] Test in user repos
- [ ] Add compat entries in project for new deps
- [ ] Add docs page

Start by reading the linked ClimaCoupler.jl Checkpointer.jl, ClimaAtmos callbacks.jl, and checkpointer_tests.jl files to identify the functions, callbacks, and coverage to bring over. Compare those interfaces with ClimaUtilities.jl, then track the dependency compatibility entries, documentation page, and user-repository tests listed in the TODO. Done means the generalized module and tests pass and the documented functionality works for users.

Written by the indexing model from the issue text.