[Mobile Account Snaps] Migrate all accounts references to selectors

[owencraston]

Currently the account information is derived from the preferences controller. In order to make this migration easier we should first migrate these references into isolated selectors that will serve as the API for accessing account information. These selectors will still use the preference controller as their source of truth.

Here are the newly added selectors on the extension.

References

Here are the relevant PRs on the extension

• Add Accounts Controller metamask-extension#21437
• feat: update UI elements to use getSelectedInternalAccount selector metamask-extension#21553
• feat: update selectors to include internal accounts metamask-extension#21554
• feat: replace use of getMetaMaskIdentities with getInternalAccounts metamask-extension#21709

[gantunesr]

From a discussion with @owencraston,

1. Replace all direct calls to the preferences-controller state (selectedAddress or identities) to either a selector or the useAccounts hook depending on the case. This should be also a good opportunity to add unit test in critical parts if they're missing.
2. Resolve the inconsistency regarding importTime between the data type in the accounts-controller and preferences-controller. The easiest option is to use the preferences-controller data. Important to take into consideration a similar approach as extension of blocking the user of adding duplicated accounts
3. Change the preference-controller selectors to accounts-controller selectors (selectSelectedAddress or selectIdentities).

Considerations,

• Keep in mind the InternalAccountStruct against the Identity type