fix: trn1 instance family does not support volume size

[evakravi]

Issue #, if available:

Description of changes:
When a trn1 instance family is used, the PySDK would automatically use volume size argument when creating the endpoint config. However, this instance family does not support attaching an ebs volume, hence volume size argument throws a service exception. This PR updates the volume_size_supported function to correctly identify trn1 instance types as not supporting volume size.

Testing done:
Unit tests added.

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[yusharon]

unsupported_families = ["g5", "g6", "p5", "trn1"]
return not any(family.startswith(prefix) for prefix in unsupported_families)

not a blocker, but I think it might be more concise to write it as above.

[evakravi]

thanks, i agree that that's def a better organization