Merge bitcoindevkit/bdk#614: Avoid using immature coinbase inputs

e85aa247cb Avoid using immature coinbase inputs (Daniela Brozzoni)
0e0d5a0e95 populate_test_db accepts a `coinbase` param (Daniela Brozzoni)

Pull request description:

  ### Description

  With this PR we start considering how many confirmations a coinbase has. If it's not mature yet, we don't use it for building transactions.
  Fixes #413

  ### Notes to the reviewers

  This PR is based on #611, review that one before reviewing this 😄

  007c5a78335a3e9f6c9c28a077793c2ba34bbb4e adds a coinbase parameter to `populate_test_db`, to specify if you want the db to be populated with immature coins. This is useful for `test_spend_coinbase`, but that's probably going to be the only use case.
  I don't think it's a big deal to have a test function take an almost_always_useless parameter - it's not an exposed API, anyways. But, if you can come up with a different way of implementing `test_spend_coinbase` that doesn't require 007c5a78335a3e9f6c9c28a077793c2ba34bbb4e, even better! I looked for it for a while, but other than duplicating the whole `populate_test_db` code, which made the test way harder to comprehend, I didn't find any other way.

  ### 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

  #### Bugfixes:

  * [ ] This pull request breaks the existing API
  * [x] I've added tests to reproduce the issue which are now passing
  * [x] I'm linking the issue being fixed by this PR

ACKs for top commit:
  afilini:
    ACK e85aa24

Tree-SHA512: 30f470c33f9ffe928500a58f821f8ce445c653766459465eb005031ac523c6f143856fc9ca68a8e1f23a485c6543a9565bd889f9557c92bf5322e81291212a5f

src/database/memory.rs

@@ -482,15 +482,23 @@ impl ConfigurableDatabase for MemoryDatabase {
 /// don't have `test` set.
 macro_rules! populate_test_db {
     ($db:expr, $tx_meta:expr, $current_height:expr$(,)?) => {{
+        $crate::populate_test_db!($db, $tx_meta, $current_height, (@coinbase false))
+    }};
+    ($db:expr, $tx_meta:expr, $current_height:expr, (@coinbase $is_coinbase:expr)$(,)?) => {{
         use std::str::FromStr;
         use $crate::database::BatchOperations;
         let mut db = $db;
         let tx_meta = $tx_meta;
         let current_height: Option<u32> = $current_height;
+        let input = if $is_coinbase {
+            vec![$crate::bitcoin::TxIn::default()]
+        } else {
+            vec![]
+        };
         let tx = $crate::bitcoin::Transaction {
             version: 1,
             lock_time: 0,
-            input: vec![],
+            input,
             output: tx_meta
                 .output
                 .iter()