Improve markup of the BuddyPress Tools screen

[mercime]

To do:

1) Combine two fieldsets into one.
2) Remove table layout in fieldset.
3) Add style support.

[mercime]

Desktop

[mercime]

Mobile

[DJPaul]

I'm not sure I agree that each sentence needs to be its own paragraph from a reading-the-words perspective. I think the way it was, plus moving the "Use the tools" to its own paragraph like you've done, is better.

[mercime]

Thanks @DJPaul. I agree. The change in wp-admin font from Open Sans to the Windows default font has made reading long lines`difficult. I was going for this layout ​https://cldup.com/QsGvaTCA9I.png where text is more legible.

Attaching new patch along with screenshots based on your feedback plus some style tweaks: add max-width to the page wrapper and increased line-height for desktop view.

[mercime]

In 11014:

Improve markup of the BuddyPress Tools screen.

Make the screen accessible:

• remove an extra fieldset
• remove table markup from fieldset
• improve legibility of long text for desktop

Fixes #7219.