Add go back button to Confirm wallet encryption window, add cancel button to wallet to be encrypted window

[jarolrod]

When i go to create a wallet, I have the option to encrypt my wallet. If i choose this option, the next step is to choose a password.
ok 👍, I've chosen a password. Now, I click on the Ok button to continue to the next screen which is the following warning:

Now i have been reminded with the life changing knowledge that if I lose this passphrase then I lose all of my Bitcoin. I now have to think about whether or not the wallet I have chosen is what i want it to be. If I am still content with my wallet, then I can continue on. If i am not content with my password, I cannot go back and change it. Instead, I have to click the Cancel button and start all over. The Confirm wallet encryption wallet should introduce a go back button that allows me to 'go back' to the Encrypt Wallet window.

Additionally, the Cancel button in this window can be removed. If we go back we can cancel in the Encrypt Wallet window, if we go forward -> read on ...

If I was content with my wallet password I can continue on. The next window is another message reminding me that wallet is going to be encrypted and that this does not fully protect my Bitcoin from being stolen:

If I am content with this security assumption I can continue on, but at this stage there is no option to be able to cancel my creation of this wallet. The Wallet to be encrypted window should introduce a Cancel button that 'cancels' the creation of this wallet.

[maflcko]

See also bitcoin/bitcoin#18085

[hebasto]

A bit related #151.

[hebasto]

@jarolrod

Mind reviewing #722?