Implement picking dynamic installation device

[frelon]

This PR adds the implementation for picking the installation device during registration based on a deviceSelector in the MachineRegistration.

Pasting some example registrations for different use-cases:

# Install to /dev/sda, /dev/vda or /dev/nvme0, whichever is found first
apiVersion: elemental.cattle.io/v1beta1
kind: MachineRegistration
metadata:
  name: fire-nodes
  namespace: fleet-default
spec:
  config:
    elemental:
      install:
        device-selector:
          - key: Name
            operator: In
            values:
            - /dev/sda
            - /dev/vda
            - /dev/nvme0

# Install to any device with a size between 80Gi and 200Gi
apiVersion: elemental.cattle.io/v1beta1
kind: MachineRegistration
metadata:
  name: fire-nodes
  namespace: fleet-default
spec:
  config:
    elemental:
      install:
        device-selector:
          - key: Size
            operator: Lt
            values:
            - 200Gi
          - key: Size
            operator: Gt
            values:
            - 80Gi

Fixes #543

[codecov]

Codecov Report

Attention: 73 lines in your changes are missing coverage. Please review.

Comparison is base (c546933) 54.45% compared to head (896195e) 54.27%.

Files	Patch %	Lines
api/v1beta1/zz_generated.deepcopy.go	0.00%	33 Missing and 1 partial ⚠️
pkg/install/install.go	55.84%	27 Missing and 7 partials ⚠️
cmd/register/main.go	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #561      +/-   ##
==========================================
- Coverage   54.45%   54.27%   -0.19%     
==========================================
  Files          39       39              
  Lines        5891     6005     +114     
==========================================
+ Hits         3208     3259      +51     
- Misses       2409     2466      +57     
- Partials      274      280       +6     

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[davidcassany]

Nice, looks great to me 👍