Align issue-title-buttons with list-header

[silverwind]

This change concerns the "Edit" and "New Issue" button on top right. With this change, switching from the issue list into an issue, the "New Issue" button will no longer "shift" from the postion on the previous page.

[silverwind]

Found a slightly better fix. By removing align-items: center from the parent, we achieve the same outcome of start-aligned flex children.

[wxiaoguang]

Then it mis-aligns

[silverwind]

I guess we can attempt to center single-line title with the buttons. Button position is fine, so the text has to move.

[wxiaoguang]

-> Refactor view issue & comment list styles #35061

[silverwind]

#35061 does not do anything regarding the "New Issue" button moving down when navigating from issue list to issue.

[wxiaoguang]

Really? After "merge with main branch", this PR doesn't provide any other changes.

[wxiaoguang]

And I don't think it is a must to align components between pages.

For example: if there is "pinned issues", then the "New Issue" button also jumps.

---

If you'd like to align "everything", you need to align the issue list page's top search bar (including the search input and "New Issue" button) and the issue title line, to make them have the same "visual" height and "visually" center aligned.

[silverwind]

Pushed a different tweak, now text is centered and button does not shift on page switch. And yes I'm only optimizing the common case with no pins and no recently-pushed notice.

[silverwind]

Also fixed the title edit toggle, nothing shifts and I was able to remove another unnecessary css rule.

[silverwind]

#35061 was not backported, so this likely can't either.