Provide Oracle instances with a subnet id to use and provide metadata to instance launch.

[uhryniuk]

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Description

The following changes allow Oracle instances to be created on a specific subnet by providing the OCID for that subnet ahead of time. This is in contrast to the existing ways of finding the subnet by name or using related objects (vcn, network client, etc).

Additionally, this PR allows for users to provide a metadata dictionary directly to the instance launch. Previously, this was limited to providing the authorized ssh keys or user data to a default metadata dictionary. The default dictionary and provided dictionary are combined to ensure backwards compatibility.

Additional Context and Relevant Issues

Often in OCI scripts, the subnet OCID is previously known and being able to directly supply it would be advantageous. While providing metadata directly is required when using other services such as OKE, where metadata must be passed to instances based on cluster configuration.

Test Steps

N/A

[uhryniuk]

Ran tox locally, and 3.8 passed. 🖖

[a-dubs]

lgtm