Ability to blacklist fingerprints attributes

### Nomad version
`Nomad v0.11.2 (807cfebe90d56f9e5beec3e72936ebe86acc8ce3)`

### Feature Request
I'd like to have the ability to blacklist fingerprints at a lower level than the module.
I'm using bash script as startup-script metadata on GCE and the whole script is displayed when I do `nomad node status --verbose `

```
os.version = 10.4
platform.gce.attr.created-by = projects/337428530273/regions/europe-west3/instanceGroupManagers/sandbox-laurent-node-app
platform.gce.attr.instance-template = projects/337428530273/global/instanceTemplates/sandbox-laurent-node-app20200610124947726900000001
platform.gce.attr.startup-script = #!/bin/bash
#
# Environment variables

....
```

So I have hundreds of lines and it's really annoying. I don't want to loose the other gce metadata either.

I tried to add this configuration but it's not working.
```
options {
"fingerprint.blacklist" = "platform.gce.attr.startup-script"
}
```

Afaik we can only blacklist fingerprinters from this list : https://github.com/hashicorp/nomad/blob/cd8c5c55bd60abc4cd2865e731b903904e421a5f/client/fingerprint/fingerprint.go#L28

Thanks,

Start with client/fingerprint/fingerprint.go, which lists the available fingerprinters, and trace how the existing fingerprint blacklist option is parsed and applied. Verify the behavior with the GCE metadata example: the startup-script attribute should be omitted while the other platform.gce attributes remain visible in nomad node status --verbose.

Written by the indexing model from the issue text.