Merge bitcoindevkit/bdk#1179: build(esplora): Add async-https-rustls flag to esplora client

6817ca9bcb ci: pin hyper-rustls version to 0.24.0 for 1.57 MSRV (thunderbiscuit)
4ee41dbc40 build(esplora): Add async-https-rustls flag to esplora client (thunderbiscuit)

Pull request description:

  ### Description
  The bdk_esplora crate currently doesn't expose the [`async-https-rustls` flag offered by the rust-esplora-client](ef1925e1ee/Cargo.toml (L44)) crate and instead requires users to build using the `default-tls` flag on reqwest, which uses the platform-specific openssl library when compiling. This creates complications for cross-compilation, notably for our Android builds that currently support 3 architectures (`arm64-v8a`, `armeabi-v7a`, and `x86_64`). In order to solve this we can either compile the openssl libraries for each of the platforms we want to support, or use the rustls-tls version of reqwest. The second options is much easier and requires less fiddling with the internals of the Android native development kit and cross-compilation rabbit holes.

  Before we merge this I want to make sure I understand the tradeoffs between the `native-tls` and the `rustls-tls` and confirm that there are not potential issues there, but from what I understand they should provide the same functionality/security, and because these are already available/exposed in reqwest and rust-esplora-client, I think this should be a fairly straightforward additional feature we offer.

  ### Changelog notice
  ```txt
  Added:
    - New async-https-rustls feature flag for the bdk_esplora crate, allowing to compile rust-esplora-client using rustls-tls instead of the default native-tls.
  ```

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

ACKs for top commit:
  notmandatory:
    ACK 6817ca9bcb
  realeinherjar:
    ACK 6817ca9bcb
  danielabrozzoni:
    ACK 6817ca9bcb

Tree-SHA512: 1d417da7cf85e157d71f56442a06e817e8741822d7bff9089f7fbb70ff8b4854f1f52befbc348b849e9c98cae848b792d426cd5bf551e7a9089b15467d28efdd

crates/esplora/Cargo.toml

@@ -30,4 +30,5 @@ default = ["std", "async-https", "blocking"]
 std = ["bdk_chain/std"]
 async = ["async-trait", "futures", "esplora-client/async"]
 async-https = ["async", "esplora-client/async-https"]
+async-https-rustls = ["async", "esplora-client/async-https-rustls"]
 blocking = ["esplora-client/blocking"]