[Client] Fix UserIdentity for CertificateIdentifer & add parameter for console reference client to specify UserCertificate

[romanett]

Proposed changes

• Fix the UserIdentity constructor to load the private key of a provided certificateIdenifier.
• make UserIdentity constructor throw a ServiceResultException when a Certificate with no private key is specified.
• extend console reference client with two new parameters:
  -uc Thumbprint of a user certifiate located in the TrustedUserCertificatesStore
  -ucp Password of the private key of the user certificate
• add documentation for console reference client

Related Issues

• Fixes Improve console client sample with user certificate support #2615

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which adds functionality)
• Test enhancement (non-breaking change to increase test coverage)
• Breaking change (fix or feature that would cause existing functionality to not work as expected, requires version increase of Nuget packages)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc.
• I have signed the CLA.
• I ran tests locally with my changes, all passed.
• I fixed all failing tests in the CI pipelines.
• I fixed all introduced issues with CodeQL and LGTM.
• I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• I have added necessary documentation (if appropriate).
• Any dependent changes have been merged and published in downstream modules.

Further comments

Tested with a Certificate created with XCA.
Public Key was exported as DER
Private key was exported as PEM without PW and also as PFX with a password.
Both work as a user identity token.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 47.94%. Comparing base (91ef753) to head (f486750).

Files	Patch %	Lines
Stack/Opc.Ua.Core/Stack/Client/UserIdentity.cs	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2624      +/-   ##
==========================================
- Coverage   54.66%   47.94%   -6.72%     
==========================================
  Files         343      328      -15     
  Lines       65218    63782    -1436     
  Branches    13354    13056     -298     
==========================================
- Hits        35653    30582    -5071     
- Misses      25685    29722    +4037     
+ Partials     3880     3478     -402     

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[mregen]

nit: sure

[mregen]

nit: Certificate

[mregen]

great sample and bug fix.