Merge bitcoindevkit/bdk#657: Release 0.20.0

46c344feb02e2ecfdc065d85cba320d06811bedf Bump version to 0.20.1-dev (Steve Myers)
78d26f6eb3dcccd791a858cfc6c8303b409e9a6e Bump version to 0.20.0 (Steve Myers)
92b9597f8b8dc3694508062b5e7c5f23acbc3a4f Rename `set_current_height` to `current_height` (Alekos Filini)
b5a120c649a17302f3825c45efd9ea0c3b2dd266 Missing newlines (Alekos Filini)
af6bde3997ac2fe4cfdbb691f2af2e802f0ab7c6 Fix: Wallet sync may decrement address index (志宇)
45db468c9be0c8bb2dc5fac52fbd52b6b41b4d53 Deprecate `AddressValidator` (志宇)
01141bed5ab1f73feade4058d9488c7a12f025a8 Update CHANGELOG and lib.rs docs version (Steve Myers)
87e864674367172022feaa6d3cf5e746caa3124c Bump version to 0.20.0-rc.1 (Steve Myers)

Pull request description:

  Proposed tweet:

  📢 Release 0.20.0 is out! Highlights include bug fixes for the ElectrumBlockchain and descriptor templates, discourage fee sniping in tx building, and new tx signing options. A big thanks to our past and latest new contributors. For all changes see: https://github.com/bitcoindevkit/bdk/releases/tag/v0.20.0

ACKs for top commit:
  afilini:
    ACK 46c344feb02e2ecfdc065d85cba320d06811bedf

Tree-SHA512: 7c36a85611f715d76a37d5a285bc72f1a06297fc06b85cca7e38c3350fcbc0a3e35d38ce617a82d191538776aa49362e523beef70bbe3b93b21d8d28d774b75f