Remove network observer module

[nickgarfield]

This PR removes the network observer module from the plugin. The network observer was designed to listen for changes to accounts belonging to the network program. It would then cache these accounts in memory and use them to in the transaction execution flows. We began noticing issues a few days ago (see ticket below for details) where this cached data was stale or incorrect. This would cause a worker would think it's in the pool even when it is not. Or visa versa, a worker would think it's not in the pool when it is.

Looking at transaction histories, it's still clear why the cached account data was incorrect. The only theory that makes sense to me is that workers can sometimes be on the bad fork and when jumping to the correct fork, account updates are not pushed to geyser. This theory is not confirmed, but in the meantime this PR serves as a fix for the issue. Instead of relying on the cached account data, this PR updates the plugin to simply use the client to fetch the fresh account data for registry, pool, and snapshot accounts.

https://linear.app/clockwork-xyz/issue/CLO-122/workers-not-recognizing-pool-position-updates

[nickgarfield]

I have this deployed on the mainnet nodes, and all looks good. Will continue monitoring for a few more hours and if things continue to look good this evening, we can land.