provider-generator: deterministic dedupe strategy for provider-function name collisions (replace hard-fail)

[so0k]

Context

Follow-up from PR #296 review (jsteinich). The generator currently hard-fails with an actionable error when provider-function names collide after sanitization: two functions to one method name, a function landing on a reserved wrapper member (constructor, providerLocalName), two parameters to one identifier, or a provider config attribute colliding with the generated functions getter. The reviewer accepted this "to start with" but flagged it as a long-term support risk: a provider release introducing a collision turns into a deterministic cdktn get / prebuilt-regeneration failure.

Evidence the risk is currently theoretical: the RFC-04 collision sweep (cdktn-planning branch rfc04/collision-sweep) ran the exact compiled sanitizers against all 29 catalog providers + Grafana + MongoDB Atlas — 31/31 clean.

Scope

• Design a deterministic dedupe (e.g. suffix rules with emitted diagnostics, mirroring uniqueClassName's approach but loudly) to replace the hard-fail so a colliding upstream release degrades to a discoverable rename instead of a generation failure.
• Evaluate adopting jsii's per-language reserved-word lists proactively in the generator-side table (jsii currently handles these at compile time behind --silence-warnings reserved-word).
• Wire the collision sweep into the drift-check story (In-repo consistency check for the provider-feature availability matrix and its hand-maintained maps #309) so a colliding provider release is caught before it breaks users.

Relations: #296, #309, cdktn-planning rfc04/collision-sweep.