feat: Update provision.sh to detect arch

[Callisto13]

edit: Actually realised I don't like the flags and that the idea in #549 is correct: we should detect.

Also take care of any backwards compatibility for those downloading earlier firecracker versions which were named differently.

Closes #376
Closes #548

[Callisto13]

Reminder to make FC release a non-pre release after this is merged

[codecov-commenter]

Codecov Report

Base: 56.53% // Head: 56.61% // Increases project coverage by +0.07% 🎉

Coverage data is based on head (da9fd20) compared to base (67a19de).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #552      +/-   ##
==========================================
+ Coverage   56.53%   56.61%   +0.07%     
==========================================
  Files          57       57              
  Lines        2768     2768              
==========================================
+ Hits         1565     1567       +2     
+ Misses       1061     1059       -2     
  Partials      142      142              

Impacted Files	Coverage Δ
infrastructure/containerd/event_service.go	59.64% <0.00%> (+3.50%)	⬆️

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