fix: lazy connection pools for dynamic routing service

[prajjwalkumar17]

Type of Change

• Bugfix
• New feature
• Enhancement
• Refactoring
• Dependency updates
• Documentation
• CI/CD

Description

Previously hyperswitch server was panicking, if it wasn't able to establish a connection with dynamic_routing service. We have fixed this by establishing lazy connection pools and not established channel(which was previously). Which will insure hyperswitch server to run even when the connection isn't established.

Additional Changes

• This PR modifies the API contract
• This PR modifies the database schema
• This PR modifies application configuration/environment variables

Motivation and Context

How did you test it?

Tested on my local.

This can't be tested on Integ as we don't have this service on integ.
Can't be tested on sbx as well, as it will require the pods to be killed. and a re-establishment of connection.

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code
• I added unit tests for my changes where possible

[semanticdiff-com]

Review changes with SemanticDiff.

Analyzed 1 of 3 files.

Overall, the semantic diff is 22% smaller than the GitHub diff.

	Filename	Status
❔	Cargo.lock	Unsupported file format
❔	crates/external_services/Cargo.toml	Unsupported file format
✔️	crates/external_services/src/grpc_client/dynamic_routing.rs	21.85% smaller