feat: As a gateway user, I want adaptive rate limiting per consumer, so that abnormal traffic spikes can be automatically controlled

### Description

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## Problem

Current rate limiting plugins such as limit-req, limit-count, and limit-concurrency use static thresholds. These limits work well for predictable traffic, but they do not adapt when a specific consumer suddenly changes behavior.

In real-world scenarios, abuse or misconfiguration often appears as sudden traffic spikes from an otherwise normal consumer. With static limits, operators must manually adjust configurations or rely on external monitoring systems.

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## Proposed Feature

As a gateway user, I want an optional adaptive rate limiting mode per consumer, so that the gateway can automatically respond to abnormal traffic patterns without constant manual intervention.

This could work at a high level as follows:

- Track a rolling request baseline for each consumer (e.g., average over a recent time window).

- Detect abnormal spikes compared to the historical baseline.

- Temporarily tighten rate limits when abnormal behavior is detected.

- Gradually relax limits once traffic returns to normal patterns.

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## Why This Is Useful

- Improves security by mitigating sudden abuse patterns.

- Reduces operational overhead for gateway operators.

- Adds intelligent traffic control at the gateway level.

- Enhances production-grade resilience without external systems.

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## Possible Direction

- This could potentially be implemented:

- As an extension to existing rate limit plugins, or

- As a separate plugin (e.g., adaptive-limit)

- Using shared memory or Redis to maintain rolling consumer metrics.

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This is a feature proposal and not a duplicate of existing static rate limiting discussions. I would appreciate feedback on feasibility and design considerations and if any suggestions and guidance regarding this please guide me.

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Start by reading the existing limit-req, limit-count, and limit-concurrency plugins to understand their current static-threshold behavior. Compare an extension versus a separate adaptive-limit plugin, and evaluate shared memory or Redis for rolling consumer metrics; done requires an agreed design for detection, temporary tightening, and recovery.

Written by the indexing model from the issue text.