Add a cargo deny workflow (#89)

* Add a cargo deny workflow

Also trims out a pointless submodule checkout (we have none).

* Remove no longer relevant advisories/allowances

* Patch for array-bytes

* Remove unused properties

* Restore chrono advisory

* Allow MPL-2.0, correct GPL-3.0 allowance specification

* Properly ban copyleft, run on all crates

* Exceptions for Serai crates (AGPL-3.0)

* Remove top comments

* Clarify reasoning for not checking advisories in CI

* Run all checks in CI

While this may bring down an unrelated commit, we can manually review, before creating a followup commit allowing it. If it's critical, then this did its job.

Cargo.toml

@@ -48,3 +48,8 @@ monero-serai = { opt-level = 3 }
 
 [profile.release]
 panic = "unwind"
+
+[patch.crates-io]
+# array-bytes 4.1.0 is GPL-3.0.
+# array-bytes git, which has no code changes, includes a dual-license under Apache-2.0.
+array-bytes = { git = "https://github.com/hack-ink/array-bytes", rev = "994cd29b66bd2ab5c8c15f0b15a1618d4bb2d94c" }