Revise GCPBatch infra vs. plugin help menu and defaults

[araghukas]

Relevant PR: #32

Issue

This issue concerns the output of covalent deploy up gcpbatch --help and errors regarding e.g. covalent deploy up gcpbatch --vcpus=12. Note, the latter command fails if --key_path is not specified.

Recommended Tasks

Beta Give feedback

1. set the key_path default to /Users/<user>/.config/gcloud/application_default_credentials.json" as in .tf files.
2. set service_account_email and project_id defaults from gcloud config (see gcloud config list) if possible
3. double check agreement between infra and plugin defaults.

Consider also, changes to Covalent OS:

• distinguish/omit user-settable vs not parameters in/from help table; some param defaults a uniquely auto-generated based on the prefix (see relevant .tf files)