Use new helper to simplify escrow tests

[mikemaccana]

We have a new helper that can:

• Make a bunch of users (with SOL)
• Make a bunch of tokens
• Distribute a desired balance of tokens to PDAs for all the users

Use that to make the Escrow program smaller.

Also:

• replace copy pasted token transfer code with shared transfer_tokens() function
• fix timing warnings on tests

[mikemaccana]

Test failing, but they work locally and I can't see any errors for the failure on github, Have mentioned to @heyAyushh .