[Assets Controllers] Remove state scoped to the current chain

[bergeron]

• TokensController
• TokenListController
• AccountTrackerController

These controllers have some fields in their state scoped to the current chain, and other fields in their state keyed by chain id. The former is deprecated and should be removed in favor of querying state by chain id. Make sure all clients are using the per chain variants, deprecate the old fields, and remove any logic in the controllers that updates them.

[adonesky1]

All of these controllers also have state that is keyed (and updated) by chainId which can simply be read instead.