Fix Double Deposit Issue

[rauljordan]

Validators that have auto-deposit functionality on exhibiter some strange behavior that would cause them to deposit twice. The situation was as follows:

1. On startup, the challenge manager will attempt to auto-deposit ERC20 stake (wrap ETH to WETH)
2. The validator will then perform a new stake on a new assertion, which would transfer the WETH to the rollup contract
3. The next assertion the validator tries to post would once again attempt wrapping ETH to WETH

Instead, we skip wrapping to WETH if the validator is already staked. This PR adds a regression test that proves we only observe a single deposit event from the staker

Fixes NIT-3600

[eljobe]

Actually, looks like this broke the assertion_test.go