Improve error propagation in ApplicationSet command generation

[coderabbitai]

Description

Currently, getArgoApplicationSetCommand logs errors from getApplicationSetSourceNamespaces but continues execution, potentially creating a deployment without the --applicationset-namespaces flag. This can silently disable the ApplicationSet feature when namespace retrieval fails.

Proposed Solution

Update getArgoApplicationSetCommand to return ([]string, error) and propagate errors up to the reconciler instead of swallowing them. This will allow:

• Early return when getApplicationSetSourceNamespaces fails
• Proper error handling for getSourceNamespaces failures
• Reconciliation retry on transient errors
• Surfacing issues instead of hiding them

Scope

This change will require updates to:

• getArgoApplicationSetCommand function signature
• All callers of getArgoApplicationSetCommand to handle errors
• Related error handling logic in the reconciliation flow

Context

This improvement was identified during PR #1988 (wildcard support for ApplicationSet source namespaces) but deferred to keep that PR focused on pattern matching functionality.

References

• PR: Add Wildcards support in ApplicationSet Source Namespaces #1988
• Discussion: Add Wildcards support in ApplicationSet Source Namespaces #1988 (comment)
• Requested by: @Mangaal