Merge bitcoin/bitcoin#26886: test: add rescan utxos inside MiniWallet's initialization

6bd098a838 test: simplify tests by using the pre-mined chain (kouloumos)
42029a7fd4 test: remove redundant blocks generation logic (kouloumos)
0377d6bb42 test: add `rescan_utxos` in MiniWallet's initialization (kouloumos)

Pull request description:

  When a pre-mined blockchain is used (default behavior), it [contains coinbase outputs in blocks 76-10](07c54de550/test/functional/test_framework/test_framework.py (L809-L813)) to [the MiniWallet's default address](07c54de550/test/functional/test_framework/wallet.py (L99-L101)). That's why we always* `rescan_utxos()` after initializing the MiniWallet, in order for the MiniWallet to account for those mature UTXOs.

  > The tests following this usage pattern can be seen with:
  > ```git grep -n "MiniWallet(" $(git grep -le "rescan_utxos()" $(git grep -Le "self.setup_clean_chain = True"))```

  **This PR adds `rescan_utxos()` inside MiniWallet's initialization to simplify usage when the MiniWallet is used with a pre-mined chain.**

  ### secondary changes

  - *There are a few tests that use the pre-mined blockchain but do not `rescan_utxos()`, they instead generate new blocks to create mature UTXOs.

    > Those were written before the `rescan_utxos()` method was introduced with https://github.com/bitcoin/bitcoin/pull/22955 (fac66d0a39) and can be seen with:
    > `git grep -n "MiniWallet(" $(git grep -Le "rescan_utxos()" $(git grep -Le "self.setup_clean_chain = True"))`
    >

    After including `rescan_utxos()` inside MiniWallets initilization, this blocks generation logic is not needed as the MiniWallet already accounts for enough mature UTXOs to perform the tests. **Therefore the now redundant blocks generation logic is removed from those tests with the second commit.**

  - The rest of the MiniWallet tests use a clean chain (`self.setup_clean_chain = True`)  and can be seen with
    `git grep -n "MiniWallet(" $(git grep -le "self.setup_clean_chain = True")`

    From those, there are a few that start from a clean chain and then create enough mature UTXOs for the MiniWallet with this kind of logic:
   07c54de550/test/functional/mempool_expiry.py (L36-L40)

    **Those tests are simplified in the third commit to instead utilize the mature UTXOs of the pre-mined chain.**

ACKs for top commit:
  MarcoFalke:
    ACK 6bd098a838 🕷
  theStack:
    re-ACK 6bd098a838

Tree-SHA512: 7f9361e36910e4000c33a32efdde4449f4a8a763bb42df96de826fcde469f9362f701b8c99e2a2c482d2d5a42a83ae5ae3844fdbed187ed0ff231f386c222493

test/functional/rpc_scanblocks.py

@@ -27,7 +27,6 @@ class ScanblocksTest(BitcoinTestFramework):
     def run_test(self):
         node = self.nodes[0]
         wallet = MiniWallet(node)
-        wallet.rescan_utxos()
 
         # send 1.0, mempool only
         _, spk_1, addr_1 = getnewdestination()