go/runtime/registry: Simplify creation of provisioners

[peternose]

Something is fishy with line config.GlobalConfig.Mode.IsClientOnly() && !isEnvSGX as it doesn't make sense. Do we run client with RuntimeEnvironmentELF and without DebugDontBlameOasis flag set?

[netlify]

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[codecov]

Codecov Report

Attention: Patch coverage is 72.72727% with 9 lines in your changes missing coverage. Please review.

Project coverage is 64.91%. Comparing base (6e6677d) to head (6ab9c9e).
Report is 31 commits behind head on master.

Files with missing lines	Patch %	Lines
go/runtime/registry/config.go	75.86%	3 Missing and 4 partials ⚠️
go/runtime/registry/registry.go	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5975      +/-   ##
==========================================
+ Coverage   64.68%   64.91%   +0.22%     
==========================================
  Files         629      632       +3     
  Lines       64299    64792     +493     
==========================================
+ Hits        41594    42057     +463     
+ Misses      17796    17792       -4     
- Partials     4909     4943      +34     

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[ptrus]

Do we run client with RuntimeEnvironmentELF and without DebugDontBlameOasis flag set?

Yes I believe so: For example, running a ParaTime client node for an SGX-enabled ParaTime like Cipher doesn't require having SGX on the ParaTime client node..