Clear out loading indicator when asset discovery is not being run

[HEagle18]

Description

Issue - loading indicator keeps going at the bottom of the wallet portfolio

Please see conversation here --> https://bravesoftware.slack.com/archives/C023VS4HJ6Q/p1686164364305479

Nick's comments - ´I think the loading indicator is not being cleared in cases when asset discovery is not being run on portfolio refresh due to rate limiting. I think the frontend is waiting for an onDiscoverAssetsCompleted event that will never actually come.

The frontend might be assuming asset discovery is run on every single portfolio refresh, when it should only make that assumption when it receives a onDiscoverAssetsStarted event´

Steps to Reproduce

Actual result:

Expected result:

Reproduces how often:

Desktop Brave version:

Android Device details:

• Install type (ARM, x86):
• Device type (Phone, Tablet, Phablet):
• Android version:

Version/Channel Information:

• Can you reproduce this issue with the current release?
• Can you reproduce this issue with the beta channel?
• Can you reproduce this issue with the nightly channel?

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

[HEagle18]

@Douglashdaniel @nvonpentz to discuss exactly what's needed here.

[nvonpentz]

I think this is what's happening @Douglashdaniel

1. Every time the portfolio page is refreshed, the frontend displays the loading spinner until it receives an onDiscoverAssetsCompleted event.
2. When the portfolio page is refreshed multiple times in under a minute, the backend applies rate limiting, and does not fulfill the subsequent requests, and thus no onDiscoverAssetsCompleted event is emitted.
3. In these cases the loading spinner is not cleared until the user waits a minute and refreshes again

If that's right, then I think this can be fixed by the frontend using the onDiscoverAssetsStarted event to display the loading spinner rather than just portfolio refresh. There should be a guarantee that an onDiscoverAssetsCompleted event will follow every time. Also, there should not be any overlap, e.g. two onDiscoverAssetsStarted events in a row before an onDiscoverAssetsCompleted event.

Ref #27776

[srirambv]

Verification passed on Google Pixel 8 with Android 14 running 1.62.123 x64 Beta build

• Verified steps from brave/brave-core#20738
• Verified loading state indicator is cleared when asset discovery is complete

30921.mp4

[srirambv]

Verification passed on

Brave	1.62.130 Chromium: 120.0.6099.199 (Official Build) beta (64-bit)
Revision	6d589c6dc0f3489830d40332c82cdd5597e41c88
OS	Windows 11 Version 23H2 (Build 22631.2861)

• Verified steps from brave/brave-core#20738
• Verified loading state indicator is cleared when asset discovery is complete

30921.mp4