[Cashtab] [BCH deprecation] Pt 1/2 - Implement local generateBurnOpReturn function

Summary:
T2730

This diff adds in-app logic to generate the burn OP_RETURN script.

Test Plan:
npm test and ensure unit test passes
npm start
burn an existing and new token and ensure console displays the 'BCH-JS burn script matches the local burn script' statement
burn a full token balance and ensure the same console log is displayed and verify explorer shows no token change in output

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D12413