Community stamping config gates

[ben-malbeclabs]

Implement ShouldStamp helper covering the all / tenants / devices / exclude hierarchy from features.yaml. Used in route-map template to determine whether to stamp a given tenant on a given device.

Milestone: RFC-18: Controller — Community Stamping
RFC: #3288

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Files affected:

• controlplane/controller/internal/controller/ (ShouldStamp helper, config struct)

Size: Medium

Tests:

• all: true stamps all tenants on all devices
• Per-tenant override respected
• Per-device override respected
• Exclude list takes precedence over all and tenants

Blockers: #3353 (route-map color community template)

[ben-malbeclabs]

Implemented in #3515 (RFC-18 PR 5).