[ENH][TRA] tiki-install.tpl : Checking the correct db encoding, clarify and translate messages

Link to the Task description : https://avan.tech/item74533-Installation-Clarification-of-the-UTF-8-test-message-after-locking-the-Tiki ENH of the previous changes : !1393 (diffs)

• We're now letting the user know that the selected enconding is correct as required
• We're now making sure the selected client charset and database encoding are correct and consistent
• we're now checking that it's either utf8 or utf8mb4 enconding
• Updated the message

[TRA] "Charset" it self is translated as "jeu de caractères" but "Client Charset" will remain "Client Charset". See https://www.linguee.fr/anglais-francais/traduction/charset.html for reference