Feature Request: Support blocklist fingerprints input by file

[brad-defined]

Blocklists in the Nebula config are a list of cert fingerprints identifying certificates that should not be honored during handshakes.
Instead of only specifying the blocklist as a list of fingerprints from the Nebula config, implement a way to read the blocklist fingerprints from a file.

From Slack (https://nebulaoss.slack.com/archives/CRWJJM52B/p1700252974702429):
I think it will have to be our way of “deprovisioning” some certs and I don’t love the idea of having to programmatically modify config files just to add to the blocklist.

[3lorsin]

+1

In my use case, almost all of my hosts are snowflakes. So, being able to push a "master" blocklist file that each client points to would be much easier than manually or programmatically modifying each individual config.

If this feature is added, an example file in the docs would be nice for explaining the formatting for multiple blocked keys.