[Cashtab] Convert OP_RETURN input into TextArea

Summary:
As per T1968:

• Changed the current <Input> field for the optional OP_RETURN message into <TextArea> to ensure longer messages are visible by default.
• The <TextArea> input also shows count to assist the user in composing the size of their message.

Test Plan:

• npm start
• Navigate to Send, open the 'Advanced' section and ensure the Placeholder text is fully visible, indicating to the user that this is an optional OP_RETURN message input and is limited to 150 chars
• Send a normal XEC transaction without the OP_RETURN message and ensure no regression to existing send function
• Send message < 150 chars and ensure it is reflected in tx history and explorer
• Attempt to send message > 150 chars and ensure the <TextArea> input prevents this as well as the character counter showing 150 at the limit.
• Send message with bunch of spaces and ensure both tx history and explorer only shows a normal transation with no OP_RETURN message (useBCH.js ignores empty string messages)
• verify cross browser compatibility with Firefox
• npm run extension
• verify the above in extension mode

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D10490