[Cashtab][Alias] Move getAliasRegistrationFee into aliasUtils

Summary:
T3216

All alias related utilities are being consolidated in aliasUtils, hence moving getAliasRegistrationFee and it's helper function getAliasByteSize (only used in getAliasRegistrationFee).
Associated unit tests migrated accordingly.

Test Plan:
grep -r getAliasRegistrationFee src/ and ensure references are to aliasUtils.js
grep -r getAliasByteSize src/ and ensure references are to aliasUtils.js
npm test
set alias flag to true in Ticker.js
npm start
navigate to Alias page, input an alias and ensure the size/price preview is correct

Reviewers: bytesofman, #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14239