Merge branch 'bugfix/partition_and_mmap_issues' into 'master'

Fix partition- and mmap-related issues

- Fix unit tests failing to start up due to a mismatch between sdkconfig flash size and size required by partition table.
- Fix a bug that partition APIs loaded the partition table in reverse order. As such, `esp_partition_next` and `esp_partition_find_first` did not work as expected. Add a test.
- Update the workaround for stale cache reads issue: do Cache_Flush for non-encrypted flash as well. Add a test.

See merge request !555