Capture number of snapshots created per day as a metric

[maluchari]

Summary

Adding a metric to capture number of snapshots being created every day. This will help in understanding if there is any anomalous behavior wrt any jobs that execute on OpenHouse tables. This could also help us get a count of number of unexpired snapshots from the past.

Changes

• [ ] Client-facing API Changes
• [ ] Internal API Changes
• [ ] Bug Fixes
• [X] New Features
• [ ] Performance Improvements
• [ ] Code Style
• [ ] Refactoring
• [ ] Documentation
• [ ] Tests

For all the boxes checked, please include additional details of the changes made in this pull request.

Testing Done

Added UT to check the same.

• [ ] Manually Tested on local docker setup. Please include commands ran, and their output.
• [X] Added new tests for the changes made.
• [ ] Updated existing tests to reflect the changes made.
• [ ] No tests added or updated. Please explain why. If unsure, please feel free to ask for help.
• [ ] Some other form of testing like staging or soak time in production. Please explain.

For all the boxes checked, include a detailed description of the testing done for the changes made in this pull request.

Additional Information

• [ ] Breaking Changes
• [ ] Deprecations
• [ ] Large PR broken into smaller PRs, and PR plan linked in the description.

A minor non-breaking change.

For all the boxes checked, include additional details of the changes made in this pull request.