Allow to set the matching pool token & amount to be something other than USD

[laurenluz]

for many rounds, we will have matching pools in tokens beyond USD...

MATIC, mpETH, USDGLO, DAI, etc...

To date, all our matching pools are set as "matching pool amount in USD" - in admin bro & in the backend, and this number is used for a variety of other things including

• estimated matching
• project weight & final matching in data export
• round stats (#3674)

I would like to be able to choose a chain & a token for the matching pool (and have this set in our backend) and then set the amount in that token. We will need to consider then that we should fetch the price of the token when showing estimated matching etc.

I think this is a backend first issue.

@jainkrati