Ticket(s)

Fixes #537.

Description

In this PR I tried to address the issues raised in #537:

1. Git is now installed prior to setting the GATEWAYD_VERSION env-var.
2. There is a new env-var, ARCH, that can be used to set the architecture of GatewayD and plugins to install and it accepts two values amd64 (default) or arm64. Otherwise it'll be set automatically using uname -m command.
3. Improved exit codes based on this link, and added comments and logs, so that it's easier to spot the issue.

@sinadarbouy would be happy if you could test this PR and confirm that it works as expected. 🙏 Then, I'll merge it.
@hamedsalim1999 would be happy to have your feedback as well.

Related PRs

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Development Checklist

• I have added a descriptive title to this PR.
• I have squashed related commits together.
• I have rebased my branch on top of the latest main branch.
• I have performed a self-review of my own code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have added docstring(s) to my code.
• I have made corresponding changes to the documentation (docs).
• I have updated docs using make gen-docs command.
• I have added tests for my changes.
• I have signed all the commits.

Legal Checklist

• I have read the CONTRIBUTING document.
• I have read and understood the Code of Conduct.
• I have read and agreed to the Apache CLA (required).
• I have read and agreed to the LICENSE (required).