Rework IPAM and fix concurrent IP race conditions

[BeryJu]

Rework the inbuilt IPAM to prevent race conditions leading to the same IP being given out multiple times to different devices

closes #871

[netlify]

✅ Deploy Preview for beryju-gravity canceled.

Name	Link
🔨 Latest commit	35a30e9
🔍 Latest deploy log	https://app.netlify.com/sites/beryju-gravity/deploys/664b8f2a3a0a7f00081363ec

[codecov]

Codecov Report

Attention: Patch coverage is 69.14894% with 29 lines in your changes are missing coverage. Please review.

Project coverage is 23.45%. Comparing base (e45f056) to head (35a30e9).

Files	Patch %	Lines
pkg/roles/dhcp/ipam_internal.go	69.23%	20 Missing and 4 partials ⚠️
pkg/roles/dhcp/scopes.go	50.00%	2 Missing and 1 partial ⚠️
pkg/roles/dhcp/leases.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1030      +/-   ##
==========================================
+ Coverage   23.26%   23.45%   +0.18%     
==========================================
  Files         215      215              
  Lines       15617    15661      +44     
==========================================
+ Hits         3634     3673      +39     
- Misses      11555    11564       +9     
+ Partials      428      424       -4     

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