Improve check integrity naming and look

[BPerlakiH]

Solving the first points from #1391:

• The overall feature is an "ZIM file integrity check", not a "validation". The code vocabulary should be changed
• The button label should be changed from "Validate" to "Check ZIM archive integrity"
• The result entry should not be mixed with the multimedia content details but put just above the button, together in a section. The label should be changed from "valid" to "ZIM archive integrity".

iPad

macOS

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.59%. Comparing base (ceb4828) to head (a1b5340).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1394   +/-   ##
=======================================
  Coverage   92.59%   92.59%           
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  Files          18       18           
  Lines         878      878           
=======================================
  Hits          813      813           
  Misses         65       65           

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[kelson42]

• * On iPad, the look & feel of screenshot #3 is good and should be kept during the check itself. Which means, also keeping the "Cancel" putting to interrupt the test.
• * "Checking ZIM file..." dialog title seems to me to be a bit redundant with the button "Check ZIM archive integrity". I wonder if we would not better just get rid of it.
• * I would like to merge the two about "Check ZIM archive integrity". We would get only one line/entry with the following items from the left to the right (LTR language): label "ZIM archive integrity", then in the middle a button "Check/Re-check" and at the right the icon.
• * If you write the title of a book, please put it between double quote

[BPerlakiH]