Add map diff comparator to Python API

[EnricoMi]

This allows for map comparators like DiffComparators.map(Integer(), LongType()) in Python.

Fixes #225.

[github-actions]

Test Results

   618 files  ±  0     618 suites  ±0   1h 41m 53s ⏱️ +37s
   498 tests +  4     498 ✅ +  4   0 💤 ±0  0 ❌ ±0 
18 960 runs  +160  18 896 ✅ +160  64 💤 ±0  0 ❌ ±0 

Results for commit 4ae5c9c. ± Comparison against base commit 7606d00.

This pull request removes 4 and adds 8 tests. Note that renamed tests count towards both.

uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator - keyOrderSensitive=false - codegen enabled=false
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator - keyOrderSensitive=false - codegen enabled=true
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator - keyOrderSensitive=true - codegen enabled=false
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator - keyOrderSensitive=true - codegen enabled=true

uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator typed - keyOrderSensitive=false - codegen enabled=false
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator typed - keyOrderSensitive=false - codegen enabled=true
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator typed - keyOrderSensitive=true - codegen enabled=false
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator typed - keyOrderSensitive=true - codegen enabled=true
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator untyped - keyOrderSensitive=false - codegen enabled=false
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator untyped - keyOrderSensitive=false - codegen enabled=true
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator untyped - keyOrderSensitive=true - codegen enabled=false
uk.co.gresearch.spark.diff.DiffComparatorSuite ‑ map comparator untyped - keyOrderSensitive=true - codegen enabled=true

♻️ This comment has been updated with latest results.