[router] fix grpc connection conversion and add optimization

[slin1237]

Checklist

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[gemini-code-assist]

Summary of Changes

Hello @slin1237, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refines the gRPC client's connection handling within the router. It streamlines the process of converting gRPC endpoint URLs and, more significantly, implements a suite of optimizations for the underlying gRPC connections to improve their reliability and throughput.

Highlights

• gRPC Endpoint Conversion: Simplified the conversion of 'grpc://' endpoints to 'http://' by using direct string replacement, removing the more complex URL parsing logic and associated warning.
• gRPC Connection Optimizations: Introduced several 'tonic' channel configurations to enhance gRPC connection stability and performance, including HTTP/2 keep-alive, TCP keep-alive, TCP no-delay, adaptive windowing, and increased initial stream/connection window sizes.

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[gemini-code-assist]

Code Review

This pull request fixes an issue with gRPC endpoint string conversion and adds several performance optimizations to the tonic channel configuration. The changes are a good improvement.

I've left two comments:

1. A high-severity issue with the use of String::replace for changing the URL scheme, which could lead to invalid URLs. I've suggested using strip_prefix for a safer implementation.
2. A medium-severity suggestion to extract the new hardcoded channel configuration values into named constants to improve code readability and maintainability.