Use logging rather than printlns

Rather than using print statements to communicate certain events, we should be using logging. For example:

```rust
debug!("Successfully opened TDX device: {:?}", tdx_dev);
```

_Originally posted by @sandlbn in https://github.com/IntelLabs/tdx-workload-attestation/pull/1#discussion_r2065352061_

The issue names no files or tests; start by locating the print statements that communicate events and checking how logging is currently configured. Replace the relevant prints with logging such as the shown debug message, then verify that those events still appear through the project's logging output.

Written by the indexing model from the issue text.