Migrate all documentation for all map functions from scalar_functions.md to code #13021

Is your feature request related to a problem or challenge?

https://datafusion.apache.org/user-guide/sql/scalar_functions.html#map-functions

• map
• make_map
• map_extract
• map_keys
• map_values

As part of #12740 this ticket is to migrate all the existing documentation for the above named functions from the static documentation to code and to remove them from the static file.

Note that make_map is special and is not a UDF and likely should be handled on a special page. see #12948 (comment)

Here is the current static content:

doc source: https://github.com/apache/datafusion/blob/main/docs/source/user-guide/sql/scalar_functions.md
rendered: https://datafusion.apache.org/user-guide/sql/scalar_functions.html
Code source: https://github.com/apache/datafusion/tree/main/datafusion/functions-nested
Need Functions:
(see source)

Describe the solution you'd like

One (or more) PRs that

port the documentation for the above named functions from the static docs to code
Bonus points: add sql examples should be added for all functions
Remove the documentation from the static docs
Run ./dev/update_function_docs.sh to update the dynamic documentation
Here are some example PRs of doing this:

#12840 from @jonathanc-n
Migrate documentation for all string functions from scalar_functions.md to code #12775 from @Omega359
#12742

Describe alternatives you've considered

No response

Additional context

No response