aacs: new freemkv-unlock-aacs plugin crate

The AACS host-certificate bus-auth unlocker as a first-class external plugin,
peer to freemkv-unlock-ld and freemkv-unlock-css. AacsUnlocker impls
libfreemkv::Unlocker — matches DiscKind::Aacs, self-guards against the hardware
(refuses NotApplicable without issuing a handshake CDB if the drive reports a
non-Blu-ray profile), gathers host certs from the scan options, and runs the
libfreemkv cert-handshake primitive to learn the Volume ID + bus key. libfreemkv
keeps the handshake + AACS content decryption; this crate owns the unlocker.
Additive: a consuming binary opts in with one register_unlocker(...) line.

aacs/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "freemkv-unlock-aacs"
+version = "1.2.0"
+edition = "2024"
+rust-version = "1.86"
+license = "AGPL-3.0-only"
+description = "AACS host-certificate bus-auth unlocker plugin for libfreemkv (Blu-ray / UHD)"
+repository = "https://github.com/freemkv/freemkv-unlock"
+
+[dependencies]
+libfreemkv = "1.2.0"
+tracing = "0.1"