[Cashtab] Disable cash address highlighting and copying

Summary:
Addressing T1816:

• Updated QRCode.js with cross browser disabling of user selection/copying of the cash address text across CustomInput, PrefixLabel and AddressHighlightTrim styles.
• UI snapshots updated for Wallet.test.js

Test Plan:

• npm start
• navigate to Wallet and ensure you are unable to select/highlight the cashaddress text
• check the onclick function still returns the correct cash address
• check other unrelated text on the screen can be selected and highlighted
• npm run extension
• ensure the disabled select/highlight function is consistent in browser extension mode
• test the above steps across both Chrome and Firefox browsers

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D10323