Allow users to send to contract addresses as well as stacks addresses

[314159265359879]

When a user adds a contract address to the "address" field it says "invalid address", technically it is a valid principle and we could allow this.

When a user adds a contract address we could show a warning, to make sure it is their intention. If a contract does not have functions to get the tokens out they could be stuck forever.

Workaround: use the cli to send tokens to the contract instead.

[linear]

LEA-2125 Allow users to send to contract addresses as well as stacks addresses

[314159265359879]

A dev requested this feature for testing purposes:

[pete-watters]

@314159265359879 - I can take a look at this. We have a thread for it here. Can you confirm that the format is ${STACKS_ADDRESS}.counter or can the last part be contract dependant?

[markmhendrickson]

Dupe for reference: #3011

[pete-watters]

@pradel opened an issue for this with Hiro Explorer also as the same thing happens there:
hirosystems/explorer#1913