[Cashtab] Replace hardcoded length limit with settings param

Summary: Related to task T2388. Replaced hardcoded 24 character length limit in Configure.js with a parameter in the currency object.

Test Plan:
cd web/cashtab && npm start
navigate to settings tab
attempt to rename a wallet with a string that is > 24 characters
error message should appear if string is too long

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D11332