chore: migrate library version naming convention on master

Author: thunderbiscuit

wallet/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "bdk_wallet"
 homepage = "https://bitcoindevkit.org"
-version = "1.2.0"
+version = "2.0.0-alpha.0"
 repository = "https://github.com/bitcoindevkit/bdk_wallet"
 documentation = "https://docs.rs/bdk_wallet"
 description = "A modern, lightweight, descriptor-based wallet library"