Merge #10: Add feature (parity) tests for API methods

ee8aee0 Fix clippy warnings (Elias Rohrer)
37e2142 Allow reading `BITCOIN_EXE`/`ELECTRS_EXE` env (Elias Rohrer)
e390c20 Test feature parity of API methods (Elias Rohrer)

Pull request description:

  This PR adds basic feature (parity) tests for the API methods:

  - [x] `get_tx`
  - [x] `get_tx_no_opt`
  - [x] `get_tx_at_block_index`
  - [x] `get_tx_status`
  - [x] `get_header`
  - [x] `get_merkle_proof`
  - [x] `get_output_status`
  - [x] `get_height`
  - [x] `get_tip_hash`
  - [x] `get_fee_estimates`
  - [x] `scripthash_txs`

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Tree-SHA512: dc9902ce9168664404586bdfacd10b517d754cbbe800361725352e1ee6fb0519d8010b3b71ff7e4662b129bbc313bd0cdcd1b918db84e0951c9f27334e0bdeae

Author: notmandatory

Cargo.toml

@@ -24,6 +24,10 @@ reqwest = { version = "0.11", optional = true, default-features = false, feature
 
 [dev-dependencies]
 serde_json = "1.0"
+tokio = { version = "1.20.1", features = ["full"] }
+electrsd = { version = "0.19.1", features = ["legacy", "esplora_a33e97e1", "bitcoind_22_0"] }
+electrum-client = "0.10"
+lazy_static = "1.4.0"
 
 [features]
 default = ["blocking", "async", "async-https"]