feat(account-tree-controller): add :{initialized,uninitialized} events

[ccharly]

Explanation

Adding those events so consumers can rely on this instead of :stateChange during the init phase that can trigger multiple times.

The :uninitialized one is to have a symmetric event that can be used for any kind of teardown.

References

N/A

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 communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Low Risk
Additive, opt-in messenger events with no change to existing init/clearState behavior beyond one extra publish at the end of each path.

Overview
Adds lifecycle messenger events so consumers can wait for a ready account tree without inferring readiness from repeated :stateChange during init.

AccountTreeController:initialized is published at the end of init() (and therefore after reinit()), with the full controller state as payload so listeners can bootstrap without a separate getState(). AccountTreeController:uninitialized is published at the end of clearState() with an empty payload, for symmetric teardown handling (e.g. wallet reset).

New event types are wired into AccountTreeControllerEvents and exported from the package index; unit tests assert emission timing (including that initialized does not fire on clearState and uninitialized does not fire on init).

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