feat: Implement new side rounds grants homepage

#### Description

As a cGrants user, when I visit the grants homepage during a round, I want an understandable way to digest GR12 main rounds and what "side rounds" are.

**Notes:**

We are structuring the homepage as a running list with banner descriptions. We are overhauling the Grants homepage at a later date in order to provide a better user journey (perhaps as part of a Grants landing page).

**Design:** https://www.figma.com/file/wZtLnSb0mLPVnj8f4BkfVX/Side-Rounds-Exploration?node-id=437%3A10038

**A/C:**

GIVEN I am a user on the grants app homepage
WHEN I am looking at the active matching pools
THEN I see a title and description to the entire matching pool section as indicated by the design.

GIVEN I am a user on the grants app homepage
WHEN I am looking at the active matching pools
THEN I see the matching amount above "available", color-coded banners, and matching pool descriptions as indicated by the design.

GIVEN I am a Grants app internal operator on the grant brand routing policy page
WHEN I edit a grant branding policy
THEN I can edit the matching amount, hex color, and description of the matching pool banner.

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**Breakdown**

- [x] #9635
- [x] #9636