[Python] Add support MapArray to_pandas conversion

[asfimport]

MapArray does not currently support to_pandas conversion and raises a Status::NotImplemented("No known equivalent Pandas block for Arrow data of type ")

Conversion from Pandas seems to work, but should verify there are tests in place.

Reporter: Bryan Cutler / @BryanCutler
Assignee: Bryan Cutler / @BryanCutler

Related issues:

• [Python] Map data types doesn't work from Arrow to Parquet (relates to)
• [Python] Missing MapType to Pandas dtype (relates to)
• Add MapType Support for Arrow in PySpark (is depended upon by)

PRs and other links:

• GitHub Pull Request #8337

_{Note: This issue was originally created as ARROW-10151. Please see the migration documentation for further details.}

[asfimport]

Bryan Cutler / @BryanCutler:
I started working on this, I think I can have it ready for the 2.0.0 release.

[asfimport]

David Li / @lidavidm:
ARROW-9812 is similar, though that also talks about Parquet, not just Pandas.

[asfimport]

Bryan Cutler / @BryanCutler:
Thanks David, I must have missed that one. I'll keep this open for Pandas conversion.

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 8337
#8337