Enhancement

#4962 support debug tool for PageStorage, and there are tools for DeltaTree data, etc. But now they needs to start the proxy for decrypting data, which brings port conflict and make it hard to use those debug tool under cloud env.

Now I have to hack the proxy code like this
https://github.com/pingcap/tidb-engine-ext/compare/raftstore-proxy-6.1...pingcap:enc_only?expand=1

We need a decryption service only mode from proxy