Add support to set `proxy` in `http` and `grpc` directives

[tusharmath]

Currently http and grpc doesn't support proxy and can only be configured via upstream. We need to change that:

Technical Requirements

• It proxy setting is configured both at upstream and at http and grpc we should prefer the one that's local over the global setting.
• Add unit tests to ensure the http/grpc client use the provided proxies for making HTTP calls.

[tusharmath]

/bounty $190

[algora-pbc[bot]]

~~## 💎 $190 bounty • Tailcall Inc.~~

~~### Steps to solve:~~ ~~1. Start working: Comment /attempt #2820 with your implementation plan~~ ~~2. Submit work: Create a pull request including /claim #2820 in the PR body to claim the bounty~~ ~~3. Receive payment: 100% of the bounty is received 2-5 days post-reward. Make sure you are eligible for payouts~~

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Attempt	Started (GMT+0)	Solution
🟢 @beelchester	Sep 16, 2024, 1:46:07 AM	WIP

[beelchester]

/attempt #2820

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[github-actions[bot]]

Action required: Issue inactive for 30 days. Status update or closure in 7 days.

[github-actions[bot]]

Issue closed after 7 days of inactivity.