[Feature] Allow for hard coded values for Declarative calls

[Data-Nexus]

Description

There are instances where subgraphs have hard coded values that get referenced (such as stablecoin contract addresses or factory a address) which are not obtainable through the event.params.

It would be nice to be able to input a static string for Declarative calls inside the manifest as released in #5264

e.g.

          calls:
            Oracle.getPrice: Oracle[event.address].getPrice('0x04068da6c83afcfa0e13ba15a6696662335d5b75') #USDC 

Are you aware of any blockers that must be resolved before implementing this feature? If so, which? Link to any relevant GitHub issues.

No response

Some information to help us out

• Tick this box if you plan on implementing this feature yourself.
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