[2.x] Fix error handling during 2FA confirmation

[ManuelLeiner]

This PR fixes the error handling during 2FA confirmation for the Inertia Stack. The Livewire Stack already works as expected.

• the error message for an invalid confirmation code will be correctly read from the form error bag, see Fortify counterpart
• texts and buttons refresh accordingly to the current confirmation state
• confirmation form resets when 2FA process
• adds an additional check to determine if the confirmation process finished

Fixes #1028

[driesvints]

Please note that we don't review draft PR's. Please mark this as ready when you're done 👍

[ManuelLeiner]

Here are some log outputs from debugging the additional check.

// initial call to /user/profile
[2022-04-05 10:05:23 (UTC+00:00)] local.DEBUG: Session old input:
[2022-04-05 10:05:23 (UTC+00:00)] local.DEBUG: Code exists in old input:  [false]

// click on 'Enable'
[2022-04-05 10:05:39 (UTC+00:00)] local.DEBUG: Session old input:
[2022-04-05 10:05:39 (UTC+00:00)] local.DEBUG: Code exists in old input:  [false]

// confirm with empty input field
[2022-04-05 10:05:51 (UTC+00:00)] local.DEBUG: Session old input:  {"code":null}
[2022-04-05 10:05:51 (UTC+00:00)] local.DEBUG: Code exists in old input:  [true]

// confirm with a wrong code
[2022-04-05 10:06:07 (UTC+00:00)] local.DEBUG: Session old input:  {"code":"123456"}
[2022-04-05 10:06:07 (UTC+00:00)] local.DEBUG: Code exists in old input:  [true]

// updating the user's name
[2022-04-05 10:06:19 (UTC+00:00)] local.DEBUG: Session old input:
[2022-04-05 10:06:19 (UTC+00:00)] local.DEBUG: Code exists in old input:  [false]

• Up until the last two log messages the 2FA columns of the user model (two_factor_secret, two_factor_recovery_codes) stay set --> works as intended
• Updating the user's name while still in the middle of 2FA confirmation resets the 2FA columns in storage --> works as intended
• Opening the profile again while still in the middle of 2FA confirmation resets the 2FA columns in storage --> works as intended

[taylorotwell]

Thanks!