fix(gcp): use "custom-4-32768-ext" machine type for gcp

[machi1990]

Closes #

Verification Steps

1. Do x
2. Do y

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation change
• [ ] Other (please specify)

[machi1990]

ping @shawkins can you've a look as well and confirm the machine types for each cloud provider. Thanks

[machi1990]

/cc @dimakis

[machi1990]

This has been tested and verified against aws and gcp. It should be good to go barring code reviews feedback ;-) @dimakis