Update how bounty amount displays

**User Story:**
As a contributor
I want to see the value of the amount in USD when pegged to USD
So that i get an accurate representation of the payout for any given bounty

**Acceptance Criteria**

**Displaying bounty amount pegged in USD**
GIVEN i am on Gitcoin.co
AND there is a bounty created pegged to USD
WHEN i navigate to the bounty explorer
OR view the details page of a bounty pegged to USD
THEN all bounties that are pegged to USD should display as: [fixed amount of USD entered on bounty creation] USD in [payout token symbol selected on bounty creation]
**Example:** 500 USD in ETH
AND this same behavior should be reflected on the Bounty details page

**Displaying bounty amount pegged to native token**
GIVEN i am on Gitcoin.co
AND there is a bounty created pegged to USD
WHEN i navigate to the bounty explorer
OR view the details page of a bounty pegged to a native token
THEN the bounty payout amount will display as ([Amount of native token entered] ETH) ([converted amount of token at that time] USD), the first value is fixed and second value is variable
**Example** (2 ETH) (6,000 USD)

**Product & Design Links:**
https://www.figma.com/file/8AFLrc4dx9xnMXUkWOAaAR/Existing-Bounties-Updates?node-id=123%3A622

**Open Questions:**
- how do we want this to look when pegged to Native token? answered in AC

**Notes/Assumptions:**