Add validation to reward address for pooling STX with Xverse and Planbetter for bitcoin rewards

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Planbetter.org only allows native segwit addresses (bc1q...) to be used (these are autofilled when using the leather wallet)

Xverse only enforces the use of wrapped segwit addresses (stating with 3...) on their stacking app, lets do the same on lockstacks so users do not get excluded for no apparent reason when they delegate with a different type of bitcoin address.

Suggestion
Lets add validation/error messaging when users try to use something else with these pools.