Apache ORC 1.7.3 release preparation

[Dongjoon Hyun]

Hi, All.

According to the Apache ORC release plan, it's time to prepare Apache ORC
1.7.3.

https://github.com/apache/orc/milestone/4?closed=1 (Due: 2022-02-15)

Please let us know if we need more patches in branch-1.7.

Thanks,
Dongjoon