Merge bitcoin/bitcoin#25379: test: use MiniWallet to simplify mempool_package_limits.py tests

f2f6068 test: MiniWallet: add `send_self_transfer_chain` to create chain of txns (Andreas Kouloumos)
1d6b438 test: use MiniWallet to simplify mempool_package_limits.py tests (Andreas Kouloumos)

Pull request description:

  While `wallet.py` includes the MiniWallet class and some helper methods, it also includes some methods that have been moved there without having any direct relation with the MiniWallet class. Specifically `make_chain`, `create_child_with_parents` and `create_raw_chain` methods that were extracted from `rpc_packages.py` at f8253d6 in order to be used on both `mempool_package_limits.py` and `rpc_packages.py`.

  Since that change, due to the introduction of additional methods in MiniWallet, the functionality of those methods can now be replicated with the existing MiniWallet methods and simultaneously simplify those tests by using the MiniWallet.

  This PR's goals are

  -  to simplify the `mempool_package_limits.py` functional tests with usage of the MiniWallet.
  -  to make progress towards the removal of the `make_chain`, `create_child_with_parents` and `create_raw_chain` methods of `wallet.py`.

  For the purpose of the aforementioned goals, a helper method `MiniWallet.send_self_transfer_chain` is introduced and method `bulk_transaction` has been integrated in `create_self_transfer*` methods using an optional `target_weight` option.

ACKs for top commit:
  MarcoFalke:
    ACK f2f6068 👜

Tree-SHA512: 3ddfa0046168cbf7904ec6b1ca233b3fdd4f30db6aefae108b6d7fb69f34ef6fb2cf4fa7cef9473ce1434a0cc8149d236441a685352fef35359a2b7ba0d951eb

Author: MacroFake