feat: Add AWS Session Token to Metadata Requests

[sai-sunder-s]

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Fixes #194738780 🦕

[generated-files-bot]

Warning: This pull request is touching the following templated files:

• README.md - README.md is managed by synthtool. However, a partials file can be used to update the README, e.g.: https://github.com/googleapis/nodejs-storage/blob/main/.readme-partials.yaml

[bojeil-google]

Thanks for putting this together! I just have a couple of suggestions.

[bojeil-google]

No issues from my end. Thanks for putting this together!

[bcoe]

Suggested change

	"img.shields.io",
	"http://169.254.169.254/latest/api/token%22"
	"img.shields.io"

This file is generated, so removing this from ignore -- I don't think we should need it unless we link to this URL somewhere in the ref docs.

[bcoe]

@sai-sunder-s this looks good to me, appologies for the slow review.