Add `--fund` flag to forc-node to pre-fund accounts

[zees-dev]

Description

To fund accounts, one must manually edit the chainspec with funded accounts.
This is a hassle as it requires understanding the chainspec, editting and persisting the file, then referencing the file in the forc-node command.
^ Also this doesn't work reliably (to be validated).

Proposed Solution

Add a --fund flag to forc-node that allows direct account funding:

forc node local --fund <account-id>:<asset-id>,<account-id>:<asset-id>

or to also support amount

forc node local --fund <account-id>:<asset-id>:<amount>,<account-id>:<asset-id>:<amount>

With an optional --fund-amount flag to override the default funding amount.

Benefits

• Simplifies testing with wallets/accounts
• Eliminates need to manually edit chainspecs