Flag functions with {sfext}, {getdata}, and {maplayer} equivalents as deprecated

[elipousson]

Many of the functions in this package have been superseded by new versions from the {sfext}, {getdata}, and {maplayer} packages. Even though there are few (if any) users for this package other than me, I'd like to follow the good practice of flagging these functions as deprecated before removing them from the package entirely as part of the process of slimming {mapbaltimore} down to just the data and data access functions – not any of the general utility functions.

[elipousson]

I made a bunch of progress integrating lifecycle deprecation flags for this in early November: 6a522a9

And some more progress today swapping get_area_data() (which called deprecated functions) for get_location_data(): 3271782

I need to double-check I got everything and then update the version number so the deprecation messages are accurate. I'll probably remove these functions when/if I put together a non-development version number release.