Test-Proxy can optionally compress request/response

[Teams discussion](https://teams.microsoft.com/l/message/19:b7c3eda7e0864d059721517174502bdb@thread.skype/1732138346189?tenantId=72f988bf-86f1-41af-91ab-2d7cd011db47&groupId=3e17dcb0-4257-4a30-b843-77f47f1d4121&parentMessageId=1732138346189&teamName=Azure%20SDK&channelName=Test-Proxy%20-%20Questions%2C%20Help%2C%20and%20Discussion&createdTime=1732138346189)

The test-proxy should support a new flag that be set when `StartRecording` is being invoked - `CompressAtRest`. (Working title)

- If set, right before the proxy writes the recording to disk, we should compress the `request` and `response` bodies of each entry.
- This means that the request and response payloads on disk will not be human readable
- When loading a recording from `StartPlayback`, these bodies should be _decompressed_ to their original format.

All of this should be entirely transparent to the users other than:

- The CompressAtRest boolean passed in StartRecording
- The files at rest will have zipped bodies

It's a actually a bit of an interesting question, because the compressed bytes will need to be encoded to some serialized format, and I'm not actually certain if that'll save us space. OR the recording won't be json anymore.