deprecate stansummary option `--autocorr`

[mitzimorris]

Summary:

Deprecate the stansummary option autocorr.

Description:

This option displays the autocorrelations for a single chain for all draws, printed to the console. If the user specifies the -c option, to save the summary as a CSV file, the autocorration information is not saved, but printed to the console.

I've never seen this feature used. If people want it, it should be its own report. It makes the code slightly more difficult to understand and therefore maintain.

Current Version:

v2.35.0