Change key config to `Password` type.

[mashhurs]

Issue description

When --debug is enabled, there might be a key leak in the debug log in Logstash-code.

How to reproduce?

# config
Config:
      input {
        stdin {}
      }
      filter {
          fingerprint {
            key => "super-secret"
          }
      }
      output {
          stdout {
              codec => rubydebug
          }
      }

# Log before change
[2022-12-05T11:15:06,403][DEBUG][logstash.plugins.registry] On demand adding plugin to the registry {:name=>"fingerprint", :type=>"filter", :class=>LogStash::Filters::Fingerprint}
[2022-12-05T11:15:06,406][DEBUG][logstash.filters.fingerprint] config LogStash::Filters::Fingerprint/@key = "super-secret"