Reorganise payments overview currency switcher, welcome message and balances card

[Jinksi]

Part of #8765

As part of the Payment Activity Card project, we are adding a new currency selector dropdown to the Payment Overview screen. This replaced the existing Balances currency selector.

This currency selector will be a page setting, at top of page and in a sticky header on scroll. It will only be available for merchants with multiple deposit currencies.

This will affect all relevant cards (e.g. Balances, Deposits, Payment activity). Note also the WooPayments logo is removed in the design, and this epic includes that work (removing the logo).

Changes to occur:

• Welcome message now appears outside the Card
• Remove the WooPayments logo on top of the page
• Replace with the Currency switcher dropdown (appears only for merchants with multi-currency setup)
  • The currency switcher should move within a sticky-header on page vertical scroll
• Remove the currency-switcher tabs from the Balance card
• Ensure that all cards except Payments Activity Card on the Payments Overview page reflect the currency switcher dropdown changes

Important

This change is not behind the Payment Activity Widget feature flag and will be launched directly.