Grant matching cap per account

[Bradymck]

Describe the bug
Currently any account potentially can pull too much from the grant pool in terms of percentage of the total pool.

To Reproduce
Steps to reproduce the behavior:

1. Create a grant when few others are doing so
2. Collect donations as an artist
3. Wait for round to complete when very little competition is present
4. Win too much of the pool 🤑

Expected behavior
We need a max percentage of grant pool as an admin setting to prevent people from pulling too much to a single account.

Additional context
This needs some thought and we can pull inspiration from how grants stack does it:
https://manager.gitcoin.co/#/round/create?

[Bradymck]

@madvas I have not thoroughly testing how this works with current model. Would love your 2 bits here.

[ginesdt]

@Bradymck this is already in place (sort of). Using the "stars" and "toggles" of the distribute page, you can tune what each user gets from the matching pool.

This was mainly designed to avoid abuses. For example, to avoid that a creator making a lot of small donations to herself gets a big piece of the matching pool cake. However, it can also be used for the purpose you are describing.

If you select 1 out of 3 stars for a user, the maximum of the total pool she can get is 33% regardless of how many donations she received. For 2 out of 3 stars the cap will be 66%, and 3 out of 3 stars they'll have no cap. Additionally, you can manually disable some donations if they do not seem legit so they don't count for the quadratic funding computation.