Update dag actions UI

[bbovenzi]

Problem:

• We had 3 different icons for backfill.
• The Run/Task clear button looked like a refresh button
• Dag Reparse and Backfill was hidden inside a menu even though there was sufficient space

Solutions:

• Move Dag actions outside of a Menu
• Change all backfill icons to the simple one we use in the grid view
• Change the Clear icon to a retry icon

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[jscheffl]

Consolidation is OK but for "Clear" I'd rather prefer to have a icon which is a bit more clear. How about using vsc/VscDebugRestart or fa/FaRedo?

[bbovenzi]

Yes, I'm not convinced of my own attempt at the Clear Icon. Here's a new one: