chore: extract TestEnv into separate crate

`TestEnv` is extracted into its own crate to serve as a framework
for testing other block explorer APIs.

Cargo.toml

@@ -7,7 +7,7 @@ members = [
  "crates/electrum",
  "crates/esplora",
  "crates/bitcoind_rpc",
- "crates/hwi",
+ "crates/testenv",
  "example-crates/example_cli",
  "example-crates/example_electrum",
  "example-crates/example_esplora",

crates/bitcoind_rpc/Cargo.toml

@@ -19,7 +19,7 @@ bitcoincore-rpc = { version = "0.17" }
 bdk_chain = { path = "../chain", version = "0.9", default-features = false }
 
 [dev-dependencies]
-bitcoind = { version = "0.33", features = ["25_0"] }
+bdk_testenv = { path = "../testenv", default_features = false }
 anyhow = { version = "1" }
 
 [features]