Add blueprint count to telemetry ping

[knolleary]

This will include platform.counts.blueprints so we get some visibility on self-hosted usage of blueprints. Note this only records how many blueprints they have - not if they are being deployed.

Ping collector already updated via FlowFuse/usage-ping-collector#28 - and deployed.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 78.60%. Comparing base (9567425) to head (4758530).

Files	Patch %	Lines
...housekeeper/tasks/telemetryMetrics/004-platform.js	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4196      +/-   ##
==========================================
- Coverage   78.61%   78.60%   -0.02%     
==========================================
  Files         286      286              
  Lines       13109    13111       +2     
  Branches     2933     2933              
==========================================
  Hits        10306    10306              
- Misses       2803     2805       +2     

Flag	Coverage Δ
backend	78.60% <0.00%> (-0.02%)	⬇️

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