feat: support parsing buffer config from params in AsyncClientConfig

[johnlanni]

Enable AsyncClientConfig to parse buffer_flush_timeout and
max_buffer_size_before_flush from the params map passed during
construction. This allows WASM plugins to configure Redis client
buffer behavior via URL query parameters.

Changes:

• Add parseUint32FromParams() helper to parse config from params map
• Parse max_buffer_size_before_flush from params (default: 1024)
• Parse buffer_flush_timeout from params (default: 3ms)
• Add header for std::numeric_limits

Usage example:
redisInit("cluster?buffer_flush_timeout=1&max_buffer_size_before_flush=512", ...)

This enables runtime configuration of Redis batching behavior for
latency-sensitive or throughput-optimized scenarios without code changes.

Co-developed-by: Claude noreply@anthropic.com

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Note

Allow AsyncClientConfig to read buffer_flush_timeout and max_buffer_size_before_flush from params, and add tests and WASM plugin usage to validate parsing.

• Redis/Config:
  • Parse buffer params from params in Redis::AsyncClientConfig (buffer_flush_timeout, max_buffer_size_before_flush) with defaults via parseUint32FromParams helper in envoy/redis/async_client.h.
  • Include <limits>; make related members initialized from parsed values.
• WASM test plugin (test_data/test_redis_call_cpp.cc):
  • Use query params in redisInit/redisCall URLs to set buffer behavior.
• Tests (test/extensions/filters/http/wasm/wasm_filter_test.cc):
  • Include envoy/redis/async_client.h.
  • Add RedisAsyncClientConfigTest to cover parsing (defaults, invalid, zero, large, overflow).

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