[perf] Unlocking Wallet hangs UI thread

[atuchin-m]

Description

Some Wallet UI task blocks UI thread for a long time during unlocking.

Steps to Reproduce

1. Create a Wallet if you don't have one;
2. Start recording chrome://tracing
3. Open brave://wallet and unlock;
4. Stop recording, check BrowserMain thread

Actual result:

A long UI task takes 254ms on MPB M1 pro.
On a low end android phone it probably takes a few seconds.

Expected result:

No long UI tasks that blocks UI

Reproduces how often:

always

Desktop Brave version:

1.68.2 Chromium: 125.0.6422.41 (Official Build) nightly (arm64)

[atuchin-m]

1. Unlocking a wallet could be a relatively usual user action (comparing to creating a new wallet).
2. 250ms is a really long time for M1 pro. For Android we probably have some ANRs because of that.

[atuchin-m]

cc @bbondy @supermassive

[supermassive]

yep, that's a known issue https://github.com/brave/brave-core/blob/v1.66.1/components/brave_wallet/browser/keyring_service.cc#L2447-L2450

[supermassive]

This brave/brave-core#23363 should make unlocking 8-10 times faster, but still blocking.
Will fix