[Cashtab] [BCH deprecation] Pt 2/2 - Deprecate BCH.SLP.TokenType1.generateGenesisOpReturn

Summary:
T2730

Depends on D12406

This diff switches the genesis OP_RETURN script generation logic to the in-app function and deprecates the bch-js function.

Test Plan:
npm test and ensure unit test passes
npm start
create a new token with no token URL value and ensure successful creation and token stats page displays the correct initial quantity and decimal places, including the default cashtab URLas token URL
create a new token with a token URL and ensure successful creation and token stats page displays the correct initial quantity and decimal places, including the user specified token URL
create a new token with an icon and ensure successful creation and validate token stats

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D12407