For #8795: remove redundant ConstraintLayout around BrowserToolbar.

[mcomella]

This is functionally equivalent to the code before this patch but should
be slightly more performant in theory because ConstraintLayout is
expensive to inflate.

The elevation and layoutParams set dynamically appeared to have no effect
with the wrapping view but broke the view when used by itself so I had
to remove them. I also updated a few other unnecessary params.

Theoretically this may have some perf benefits but I didn't see anything
outside noise levels after I took the numbers (but I didn't try very hard).

These were the perf results:

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NO CHANGES

first click
5 runs, average: 470.4
[432, 493, 504, 484, 439]

subsequent
10 runs, average: 346.7
[352, 390, 362, 337, 334, 344, 305, 315, 398, 330]

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REMOVE TOOLBAR_WRAPPER

first click
5 runs, average: 496.6
[490, 461, 443, 573, 516]

subsequent
10 runs, average: 344
[312, 352, 375, 342, 322, 380, 337, 333, 346, 341]

I suspect the first click is higher before because of the 573 outlier rather than a true regression.

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Before:

After:

Scroll before:

Scroll after:

Pull Request checklist

• Tests: This PR includes thorough tests or an explanation of why it does not
  • UI change
• Screenshots: This PR includes screenshots or GIFs of the changes made or an explanation of why it does not
• Accessibility: The code in this PR follows accessibility best practices or does not include any user facing features. In addition, it includes a screenshot of a successful accessibility scan to ensure no new defects are added to the product.
  • 😬 I'll try to test if I have time today

After merge

• Milestone: Make sure issues finished by this pull request are added to the milestone of the version currently in development.

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