Add an argument to the control function for maximum workflow size

[topepo]

So that we can modulate these messages:

ℹ The workflow being saved contains a recipe, which is 20.78 Mb in memory. If this was not intentional, please set the control setting save_workflow = FALSE.

when save_workflow = TRUE. The argument can be the Mb limit for giving this note.

We can do the same for finetune too.

[simonpcouch]

Related to #914.

[simonpcouch]

Ah, duplicate of that issue—will close in favor of that one!

[github-actions]

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