Consider adding support for tracing

**Describe the enhancement**
It'd be great if support for tracing/logs in general could be added to BDK. It's currently very hard to understand what's happening under the hood when debugging performance issues or error messages.

It'd be fantastic if BDK could integrate the [`tracing`](https://docs.rs/tracing/latest/tracing/) framework.

**Use case**
In the last few days I've had two distinct issues pop up where I'd love to have better insight into what's going on:

1. Esplora sync fails. A request sent to my Esplora backend failed with a decode error, and all I'm getting is this: `Reqwest(reqwest::Error { kind: Decode, source: Error(\"failed to parse hex\", line: 1, column: 9007) })"}`. Without any further logs that indicate more as to what's going wrong, it's very hard to debug this
2. Performance issues with large wallets. I have a large signet wallet, currently sitting at around 30 000 UTXOs. Constructing transactions here is now taking an unacceptable amount of time. I'm working on enhancements on my end wrt. how data is persisted, but again I have very little to go on. It's impossible to see which operations are taking how much time, for example.