[WIP] feat: decouple the kubeconfig

[gauron99]

Current scope

• one identity per-cluster - f.Local.Auth is a list but we do linear search for both Setting and Getting so the other input would be "dead code"
• support 3 methods of authentication - token; cert + key (inline); exec plugin
• --cluster= can be used to "clear" the stored cluster url and re-used the active context from kubeconfig

Flow

• the flow for deploy is unchanged functionally -> func deploy first time see that no cluster is set, uses active kubeconfig context (just as now in main) and tries that as fallback method. Extra addition is on successful deploy this url + creds will be stored in-house .func/local.yaml file to be re-used on further deployments if untouched therefore you can freely switch contexts around and your function will still point to that initially deployed cluster with creds (now you dont even need kubeconfig at all)

Changes

• 🎁 Add --cluster and --cluster-token flags to deploy, describe, and delete commands for direct
  cluster access without kubeconfig
• 🎁 Auto-extract and persist cluster credentials from kubeconfig on first deploy to
  .func/local.yaml — subsequent deploys work without kubeconfig
• 🎁 Support FUNC_CLUSTER and FUNC_CLUSTER_TOKEN environment variables for CI/CD workflows
• 🎁 Add cluster field to global config (~/.config/func/config.yaml) for user-wide cluster default
• 🎁 Synthesize RawConfig() on direct cluster override to support OpenShift internal registry
  credential resolution

/kind enhancement

Release Note

Added --cluster and --cluster-token flags to deploy, describe, and delete commands. Functions can now
connect to clusters directly without kubeconfig. Automatically save cluster credentials when none are set or given (usually first deploy). Supports FUNC_CLUSTER and FUNC_CLUSTER_TOKEN environment variables for CI/CD.

[knative-prow]

Skipping CI for Draft Pull Request.
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[knative-prow]

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[codecov]

Codecov Report

❌ Patch coverage is 67.44966% with 97 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.06%. Comparing base (cea1c1d) to head (5aba827).
⚠️ Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/deploy.go	40.00%	15 Missing and 3 partials ⚠️
cmd/cluster_override.go	0.00%	16 Missing ⚠️
cmd/delete.go	60.00%	11 Missing and 3 partials ⚠️
cmd/describe.go	61.29%	10 Missing and 2 partials ⚠️
pkg/functions/function.go	33.33%	11 Missing and 1 partial ⚠️
cmd/environment.go	11.11%	8 Missing ⚠️
pkg/k8s/client.go	93.81%	4 Missing and 2 partials ⚠️
cmd/errors.go	0.00%	5 Missing ⚠️
pkg/config/config.go	50.00%	2 Missing and 1 partial ⚠️
pkg/k8s/extract.go	94.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3722      +/-   ##
==========================================
- Coverage   56.92%   56.06%   -0.87%     
==========================================
  Files         181      183       +2     
  Lines       20933    21379     +446     
==========================================
+ Hits        11916    11986      +70     
- Misses       7809     8168     +359     
- Partials     1208     1225      +17     

Flag	Coverage Δ
e2e	22.35% <20.13%> (-13.80%)	⬇️
e2e go	32.23% <19.60%> (-0.54%)	⬇️
e2e node	28.06% <19.60%> (-0.42%)	⬇️
e2e python	32.60% <19.60%> (-0.52%)	⬇️
e2e quarkus	28.20% <19.60%> (-0.40%)	⬇️
e2e rust	27.62% <19.60%> (-0.39%)	⬇️
e2e springboot	26.16% <19.60%> (-0.37%)	⬇️
e2e typescript	28.17% <19.60%> (-0.44%)	⬇️
e2e-config-ci	17.53% <8.00%> (-0.36%)	⬇️
integration	17.05% <1.60%> (-0.38%)	⬇️
unit macos-14	45.28% <64.40%> (+0.29%)	⬆️
unit macos-latest	45.28% <64.40%> (+0.29%)	⬆️
unit ubuntu-24.04-arm	45.53% <64.09%> (+0.36%)	⬆️
unit ubuntu-latest	46.22% <64.40%> (+0.38%)	⬆️
unit windows-latest	45.32% <64.40%> (+0.35%)	⬆️

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