collab: Add ability to revoke LLM service access tokens (#16143)

This PR adds the ability to revoke access tokens for the LLM service.

There is a new `revoked_access_tokens` table that contains the
identifiers (`jti`) of revoked access tokens.

To revoke an access token, insert a record into this table:

```sql
insert into revoked_access_tokens (jti) values ('1e887b9e-37f5-49e8-8feb-3274e5a86b67');
```

We now attach the `jti` as `authn.jti` to the tracing spans so that we
can associate an access token with a given request to the LLM service.

Release Notes:

- N/A

crates/collab/src/llm/db/tables.rs

@@ -1,5 +1,6 @@
 pub mod lifetime_usage;
 pub mod model;
 pub mod provider;
+pub mod revoked_access_token;
 pub mod usage;
 pub mod usage_measure;