feat: Open JoinPool canvas immediately, preloader, prioritise low member pools.

[rossbulat]

Improves pool joining UX by opening the JoinPool canvas immediately and displaying a preloading state within the canvas. This prevents the user having to click the "Join Pool" button twice, once to initiate the syncing process, and another time to open the canvas.

The user is still free to close the JoinPool canvas while the performance data is being fetched - it will continue and be ready when the user opens it again.

Breakdown of changes

• New preloading state in JoinPool canvas while performance data is being fetched, with ability to open JoinPool immediately.
• Added ability to disable ButtonTabs, with custom disabled styling.
• Moved join pool loader animation to a separate styled component.
• Optimise join pool selection to promote decentralisation.
  • Fetch the lower third of pools ordered by memberCounter.
  • Ensure pools have at least 2x the minimum active stake in points value (converting to balance would be extra overhead and time to process, deemed not necessary).
• Misc polish.