Apply tweaks to Thread list as per design spec

[t3chguy]

For element-hq/element-web#21502
Fixes element-hq/element-web#21538
Fixes element-hq/element-web#21472

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This PR currently has no changelog labels, so will not be included in changelogs.

Add one of: T-Deprecation, T-Enhancement, T-Defect, T-Task to indicate what type of change this is plus X-Breaking-Change if it's a breaking change.

Preview: https://pr8149--matrix-react-sdk.netlify.app
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[codecov]

Codecov Report

Merging #8149 (7493935) into develop (371ccd7) will decrease coverage by 0.00%.
The diff coverage is 35.00%.

@@             Coverage Diff             @@
##           develop    #8149      +/-   ##
===========================================
- Coverage    28.69%   28.68%   -0.01%     
===========================================
  Files          851      851              
  Lines        49779    49788       +9     
  Branches     12658    12662       +4     
===========================================
  Hits         14282    14282              
- Misses       35497    35506       +9     

Impacted Files	Coverage Δ
src/components/views/messages/TextualBody.tsx	57.29% <0.00%> (ø)
src/components/structures/ThreadPanel.tsx	25.71% <12.50%> (-1.98%)	⬇️
src/components/views/rooms/EventTile.tsx	46.36% <44.44%> (-0.25%)	⬇️
...ponents/views/context_menus/MessageContextMenu.tsx	54.83% <100.00%> (-0.29%)	⬇️

[germain-gg]

Code looks great 👍

[janogarcia]

I've unchecked and added notes to all tasks that need some attention:
element-hq/element-web#21502 (comment)

Update the truncating behavior for the thread summary:
element-hq/element-web#21472 (comment)

[janogarcia]

Already reported/handled internally:

• 🐛 Regression: Right border of container should be 8px (instead of 14px).
• 🐛 Not fixed yet: Barely visible, the dot is almost completely cut off

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[karlicoss]

Hi, sorry if it's not the right place to ask, but figured it's the MR where this behavior was introduced.
What's the reason for truncating the width of the thread summary?

Gone through the linked issues, but not sure I understand the max-width restriction in particular. There is enough space to fit much more in the preview.
I've undone the max-width locally with Stylus extension in the meantime:

@-moz-document domain("app.element.io") {
    .mx_ThreadSummary {
       max-width: unset !important;
    }
}

Thanks!