chore: change bridge state structure to have all fields at root of state

[infiniteflower]

Explanation

This PR changes the state shape of BridgeController and BridgeStatusController to better match the standard shape with all the relevant fields at the root of state rather than behind a redundant field like state.bridgeState or state.bridgeStatusState.

It also changes the default values from undefined to null to better support Mobile efforts.

References

Changelog

@metamask/bridge-controller

• BREAKING: Data fields have been moved to the root of the state object, rather than behind a redundant field state.bridgeState
• BREAKING: Default values have been changed from undefined to null.

@metamask/bridge-status-controller

• BREAKING: Data fields have been moved to the root of the state object, rather than behind a redundant field state.bridgeStatusState
• BREAKING: Redundant type BridgeStatusState removed from exports

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've highlighted breaking changes using the "BREAKING" category above as appropriate
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

[amitabh94]

LGTM!