Improve messaging to users to backup database

Honestly, I have no objections to this, except for the lack of test coverage. Tagging for that, but otherwise I'm happy with this wording.

Addressed @tedbow's point in the merge request and added tests. So, assigning to him for final review.

I like the update page better with removing theit is strongly recommended sentence and moving it back to the next step. but i wonder would it make sense to make It is strongly recommended to back up your database and site code before you begin. a warning message? that way it would visually highlighted? at the moment the message comes after the primary button. basically the user should made up his or her mind before clicking the button. i wonder also from a screen reader perspective what if a screen reader user processed everything before the button and then “might” miss the message after the primary key because pressing the continue button?

and the sentence on the ready to update page i would split up into two. This step cannot be undone! as a separate sentence with an exclamation mark. ...before continuing,.. wouldn’t be really necessary it is already implied in the first sentence stating that the next step cannot be undone.
and i guess so it is a good idea sounds a bit inconsistent. i know back then it was the good idea sentence on the first page(dont know exact wording anymore) and the highly recommended sentence on the ready to update page. but with this cannot be undone in the sentence before and it is strongly recommended on the update page before, ending with it is a good ideasounds like it isnt that important and necessary after all. so perhaps something like the following would be more consistent concise overall:

This step cannot be undone! It is still strongly recommended to back up your database and site code in case you haven't already done so.

...and setting the status back to needs work after asking @phenaproxima on Slack

This is still relevant and actionable.

Let's address @rkoller's feedback from #10.

I think this could still be done after MVP(though would like to get it done before)

One question on the MR for you, @yash.rode 😊

Can you please post a short screencast showing that without the messenger->deleteByType() call, two messages appear? 🙏 I don't see how that's possible for the reason mentioned on the MR 🫣

Well … those "readiness checks" messages do seem pretty important. And they seem intentional. I don't see why we want to delete them? Also, are you sure that's what's happening inside the test?

Even if we have

// Delete warnings added on updater form.
    $this->messenger()->deleteByType(MessengerInterface::TYPE_WARNING);

we will still get the Readiness check messages, it will just delete This step cannot be undone! It is still strongly recommended to back up your database and site code in case you haven't already done so. message.

Hm … I'll need to manually test this then, I cannot reasonably RTBC this until I truly understand and confirm this. That'll have to wait until next week though!

1. Clarify and Strengthen the Backup Recommendation:
Solution: Make the backup recommendation clearer and more consistent across both pages.

• Start with a clear and firm recommendation. For example, update the text to:
  "It is strongly recommended to back up your database and site before beginning the update process." (Consider making this bold for emphasis.)
• Phrase this as a friendly reminder, mentioning that the update is imminent. Example:
  "The downloaded assets will be applied to your site in the next step. This action cannot be undone. Please ensure you have backed up your database and site before proceeding."

2. Ensure Backup Recommendation for Both Manual and Automatic Updates:
Solution: Add a backup recommendation for automatically triggered updates (via cron).

• Add a reminder to back up your database and site before automatic updates are triggered. This can be phrased as a part of the notification when the update is initiated automatically:
• "Before proceeding with the automatic update, ensure you have backed up your database and site."