fix: Added save_load to squarcb

[bassmang]

No description provided.

[ataymano]

Can you please add test here?
https://github.com/VowpalWabbit/vowpal_wabbit/blob/master/test/RunTests

[bassmang]

The issue here is that a vw model is not properly saved when using --squarecb because save_load was not implemented. This is how a program reacts when using when using an old vs new model (using / not using save_load to store model), and using an old vs new vw version (using / not using save_load to load model):

old model with old vw: Program runs, however does not store state of trained model
old model with new vw: Program crashes
new model with old vw: Program crashes
new model with new vw: Program runs and maintains state of trained model

[jackgerrits]

Avoid the extra copy

Suggested change

	, _model_file_version(model_file_version)
	, _model_file_version(std::move(model_file_version))

[jackgerrits]

The format check has a pointer of how to fix it: (https://github.com/VowpalWabbit/vowpal_wabbit/pull/2988/checks?check_run_id=2547671641)

fix:
	Ensure there is an upstream remote that points to: https://github.com/VowpalWabbit/vowpal_wabbit.git
	Run: "git fetch upstream"
	Run: "git diff upstream/master...HEAD -U0 --no-color | clang-format-diff -r '^.*\.(cc|h)$' -p1 -i"