Add Oracle Cloud Infrastructure (OCI) template example

[matifali]

Create a Terraform template for provisioning Coder workspaces on Oracle Cloud Infrastructure. Should include compute instances, networking, and storage configuration.

Reference: OCI Terraform Provider Documentation

[aybanda]

/attempt #201

[aybanda]

Hey @matifali, could you please take a look at the PR ? Thanks!

[matifali]

/bounty 100