create filecoin-project/vm-tests repo; generate and tag a v0 corpus

[raulk]

Once we have:

1. migrated all of chain validation cases to test vectors (message-class and tipset-class)
2. have a batch runner for generation scripts (batch runner for test vector generation scripts #189)

We should create the filecoin-project/test-vectors repo containing a version 0 of the corpus. This would contain:

• a clear README explaining how this works, with pointers to how Lotus uses this repo (test driver, CI job, etc.)
• the schema.json as it stands at that point in time.
• the message test vectors for all cases migrated from the chain validation project, generated using the batch runner.
• more + anything else that would facilitate consumption by other implementers.

[raulk]

This is in review on Lotus side: filecoin-project/lotus#3081