feat(secrets): allow changing remote superuser credentials

[Lauri "datafox" Heino (melodicore)]

Summary

The superuser credentials for managing all remote secret access files could not be changed. Now they can.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.93%. Comparing base (c8c853d) to head (466087b).
⚠️ Report is 33 commits behind head on main.

Files with missing lines	Patch %	Lines
.../kotlin/elide/secrets/impl/SecretManagementImpl.kt	11.11%	8 Missing ⚠️
...n/elide/tool/cli/cmd/secrets/ToolSecretsCommand.kt	0.00%	2 Missing ⚠️
.../kotlin/elide/secrets/impl/RemoteManagementImpl.kt	71.42%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1754      +/-   ##
==========================================
- Coverage   42.94%   42.93%   -0.02%     
==========================================
  Files         895      895              
  Lines       42415    42432      +17     
  Branches     5959     5962       +3     
==========================================
+ Hits        18216    18218       +2     
- Misses      21997    22012      +15     
  Partials     2202     2202              

Flag	Coverage Δ
jvm	42.93% <33.33%> (-0.02%)	⬇️
lib	42.93% <33.33%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...rets/src/main/kotlin/elide/secrets/SecretValues.kt	61.53% <ø> (ø)
...n/elide/tool/cli/cmd/secrets/ToolSecretsCommand.kt	1.33% <0.00%> (-0.02%)	⬇️
.../kotlin/elide/secrets/impl/RemoteManagementImpl.kt	71.42% <71.42%> (ø)
.../kotlin/elide/secrets/impl/SecretManagementImpl.kt	64.98% <11.11%> (-1.69%)	⬇️

... and 1 file with indirect coverage changes

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