Tab group outline is not rendered properly with light theme

[simonhong]

Description

Inactive tab also should have thicker bottom line when it's included in any tab group

Steps to Reproduce

1. Launch Brave
2. Create tab group via tab's context menu (Add Tab to Group)
3. Check inactive tab's bottom bottom line in the tab group

Actual result:

Expected result:

Works properly with dark theme like below.

Reproduces how often:

100%

Brave version (brave://version info)

Version/Channel Information:

• Can you reproduce this issue with the current release? yes
• 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?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

[MadhaviSeelam]

Verification PASSED using

Brave | 1.43.54 Chromium: 104.0.5112.69 (Official Build) beta (64-bit)
-- | --
Revision | 7ce2902023c722af8564068e6b26e934b83fd774-refs/branch-heads/5112@{#1213}
OS | Windows 11 Version 21H2 (Build 22000.795)

Reproducibility:

Reproduced in 1.41.100 using STR from #24095 (comment)

Confirmed tab group border thickness in light theme rendered as expected and compared with dark mode for Normal window

dark	light

Verification:

Confirmed tab group border thickness rendered as expected for Guest window, Private window and TOR window

GW	PW	TOR

[urbenlegend]

The tab outline looks great now, but can we also fix the padding and corner radius of the group labels? It's like the last thing that will make tab groups finally look polished in Brave.

For example, look at the label Test below:

The purple box surrounding the label barely has any padding against the tab outline, making it look like its merging with it. Rounding out the corners of the box will also make it more appealing and more in line with the unnamed group circles.