Add loading state indicator in select token screen

[srirambv]

Description

Add loading state indicator in select token screen

Steps to Reproduce

1. Restore a wallet with token balance
2. Lock wallet if its already unlocked
3. Go to Send screen
4. Click on Select token
5. Shows No available tokens message for a few seconds before loading the balance

Actual result:

brave_IIrJIaptnn.mp4

Expected result:

Should add a loading state indicator and also maybe rename No available tokens to No tokens availabale

Reproduces how often:

Easy

Brave version (brave://version info)

Brave	1.58.108 Chromium: 116.0.5845.114 (Official Build) beta (64-bit)
Revision	f08ffbe3ce0069ad8207b9d2d7dee38afcccc1b9
OS	Windows 11 Version 22H2 (Build 22621.2215)

Version/Channel Information:

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

Other Additional Information:

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

Miscellaneous Information:

cc: @Douglashdaniel @josheleonard @kleantzogu

[srirambv]

Verification passed on

Brave	1.60.102 Chromium: 118.0.5993.96 (Official Build) beta (64-bit)
Revision	3598a9fc6b7752181feb25caa131bc386d6d054c
OS	Windows 11 Version 22H2 (Build 22621.2428)

• Verified steps from issue description and brave/brave-core#20026
• Verified loading state indicator is shown on Send screen when token balance is being fetched

32641.mp4