hoist workflows into ggtrace_ functions

[yjunechoe]

Part of experimenting with turning some ggtrace functionality into a 1-off function that takes plot as arg

ggtrace_inspect
ggtrace_capture
ggtrace_modify

sometimes returns evaluated expr, sometimes returns the gtable, etc. Depends on if things are done for expr itself or its side effect

[yjunechoe]

Could themselves be a family of functions:

• ggtrace_inspect_n() to return how many times the method was called (just return ._counter_)
• ggtrace_inspect_which() to return idx where the method was called (i.e., return counter when cond is met)
• ggtrace_inspect_vars() to safely return values of objects from execution env at different steps
• ggtrace_inspect_return() for inspecting return value of execution env
• ggtrace_capture_fn() for capturing method at execution as a pre-filled function
• ggtrace_capture_env() for capturing method's execution environment
• ggtrace_capture_frames() for capturing the call/frame stack from the execution env (nope let's keep frame stack stuff under the hood - advanced users can hack this on their own)
• ggtrace_highjack_args() for modifying arguments passed to a method
• ggtrace_highajck_binding/s()? for modifying variables in the execution env at different steps, given a named list of exprs (too complicated without making tracer a closure - encourage usage of with_ggtrace)
• ggtrace_highjack_fn() to replace method body with a supplied function that's called with the arguments instead (nope lets just encourage making new ggprotos instead)
• ggtrace_highjack_return() for modifying return value of execution env