HDDS-8202. Fix exception handling for snapshots module

[swamirishi]

What changes were proposed in this pull request?

Exceptions handling refactoring in the snapshot code.

Please describe your PR in detail: There are quite a few places where the snapshot code just throw new RuntimeException, the patch proposes to add a custom exception to handle exceptions better.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-8202

How was this patch tested?

Refactoring changes, existing testcases and clean build should be sufficient.

[smengcl]

Thanks @swamirishi for taking care of this! When would this be out of draft?