Checkpointer module

[juliasloan25]

Create a module for saving the simulation state and restarting it, which is particularly essential for coupling.

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