[identity] redact_sensitive_data config

Summary: we'll use this config in the next diff to conditionally hide sensitive data from our logs

Test Plan:
tested in next diff by setting the config and then calling the ping RPC, which i modified to log some sensitive data. confirmed that with the config set to true, the data is redacted in the logs

will also verify that sensitive data is now redacted on prod after next prod deployment

Reviewers: ashoat, will, bartek

Reviewed By: bartek

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D12819