feat: added support for s3 bucket in provisioner (#668)

[Shubham8287]

• feat: update provisioner.proto to add methods for provisioning storage

• feat: implemented provision_storage to create a bucket and return user credentials to access the bucket

This is a provisioner side change for task /attempt #668, Steps for provisioning storage look like -

• Create a S3 bucket by appending an uuid to project_name to make it globally unique.
• Create a User to interact with the bucket
• Create a Policy and attach that to User
• Return access keys for the user, so that resource builder can access the bucket.

[Shubham8287]

@oddgrd , @chesedo I would love to get some early eye on PR to make sure I am going on right direction.
This PR addresses provisioner-side changes for adding s3 resources. I marked it as a draft as I am yet to finalize policies to grant to new users and write tests. Though, I did the end-to-end testing by making a GRPC call to provisioner server using my personal aws account.
PS: I am new to Rust, and I tried to write stuff well but there can be some cracking lines especially the error handling part as I find that a little tricky in Rust. I am looking to learn so you can go hard while reviewing :)

[iulianbarbu]

Hey @Shubham8287 ! Thanks a lot for taking a stab at S3 resource. We'll be providing some feedback soon on this PR.

[Shubham8287]

Changes has been added in #995