fix(validate): restore lax whitespace validation for customer migration

[himeshpanc]

Fixes #N/A

Motivation

Templates using spaced variable references like {{ inputs.parameters.foo }} where foo is
not declared in the template's inputs.parameters were failing validation with:

failed to resolve {{ inputs.parameters.foo }}

Upstream PR argoproj#11781 (commit 07c256085) introduced a correct bug fix
that added strings.TrimSpace(tag) in resolveAllVariables. However, some existing users were
inadvertently relying on the pre-fix behaviour, causing validation failures after upgrading.

This is an intentional, scoped revert for the akuity release-3.7.10 branch to restore the
lax v3.4.6 behaviour and ease user template migration. Not intended for upstream contribution.

Modifications

• Removed trimmedTag := strings.TrimSpace(tag) in resolveAllVariables in workflow/validate/validate.go
• Reverted all trimmedTag usages back to tag
• Non-spaced references like {{inputs.parameters.foo}} are unaffected and retain strict validation

Verification

1. Reproduced — added TestUndeclaredSpacedParamPassesValidation with a WorkflowTemplate referencing
   {{ inputs.parameters.chart-path }} (undeclared, with spaces). Confirmed it fails with
   templates.update-env: failed to resolve {{ inputs.parameters.chart-path }} on unmodified code.
2. Unfixed — applied the revert to resolveAllVariables.
3. Verified — the repro test now passes. Updated TestShouldCheckValidationToSpacedParameters
   (added by PR fix: verify whitespaced parameters in workflow templates. Fixes #11767 argoproj/argo-workflows#11781) to reflect the restored lax behaviour.
4. Full ./workflow/... test suite run — all 37 packages pass, zero failures.

Documentation

No documentation changes needed — this is a scoped internal revert, not a new feature.