MFW-5961 Added DnsFilterManager to proto file

[vishalmane09]

• Did you name your branch and commit in the right format?
• Did you raise the PR on the correct branch?
• Did you merge the target branch before creating this PR?
• Did you add unit tests for your changes
• Did you create structs instead of using interfaces
• Did you test your work
• Did you make sure to DRY your code? Were you able to refactor existing code for reuse instead of making similar code?
• Did you break your code into smaller methods or components that each have a clear, singular responsibility, and could possibly be reused?
• Did you reduce the nesting level in your code, so it is not more than three levels nested in a method? Did you return early to reduce nesting?
• Did you add comments so for instance a new developer would understand this code, and understand any business logic?
• Did you add an intranet note/page if this is new behavior/feature
• Did you resolve all conversations on the PR?

[vishal-malji]

LGTM