Don't require async when decrypting reports

[mendess]

Decrypting reports usually happens as they are consumed, which is a CPU bound
task. Not requiring async for this has a few advantages:

• it can be more easily offloaded to a thread outside the async runtime to
  prevent it from blocking the runtime
• it can be more easily benchmarked and flamegraphed, as flamegraphing async
  functions is almost impossible

[cjpatton]

Nice!