[Python] Random schema and data generator for Arrow conversion and Parquet testing

[asfimport]

See discussion in #2067

Being able to generate random complex schemas and corresponding example data sets will help with exercising edge cases in many different parts of the codebase. One practical example: reading and writing nested data to Parquet format

Reporter: Wes McKinney / @wesm
Assignee: Krisztian Szucs / @kszucs

Related issues:

• [Python] Make Schema hashable (supercedes)

PRs and other links:

• GitHub Pull Request #3046

_{Note: This issue was originally created as ARROW-2624. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
The ASV benchmark suite has some support to generate random data for some types, but not random schema.
(see the BuiltinsGenerator in python/benchmarks/common.py)

[asfimport]

Krisztian Szucs / @kszucs:
Issue resolved by pull request 3046
#3046