Fix C04 credit class metadata

[blushi]

The C04 credit class has been created on chain with some initial metadata as specified in #57

But this metadata has some issues that should be fixed:

• use regen:address instead of regen:walletAddress ruuts-c04-metadata #57 (comment)
• could we just use a @list for regen:bufferPoolAccounts? if we don't expect regen:bufferPoolAccounts to have other properties than schema:itemListElement like schema:url or schema:name, then we should just have it as a list ruuts-c04-metadata #57 (comment)
• fix misusages of types/properties from schema.org as described in ruuts-c04-metadata #57 (comment) and ruuts-c04-metadata #57 (comment)
• distinguish measured co-benefits from project benefits as specified in feat: Add support for storing impact/co-benefits and sdgs related info in anchored metadata #64

[ryanchristo]

Pending metadata for C04 from registry team.

[ryanchristo]

Hey team! Please add your planning poker estimate with Zenhub @blushi @wgwz

[ryanchristo]

Open questions still around co-benefits. Awaiting input from registry team.

[blushi]

Missing on chain C04 update