Denote more compatibility in info.xml

This proposal adds a notation for php & smarty compatibility in info.xml files as a standard - ie

Step 1 - add to core extensions , documentation Step 2 - make visible in the UI Step 3 (near future) start to push extensions to add it. Step 4 (further out future - 6 months +) filter displayed extensions based on it

It is required because in some cases extensions support less php or smarty versions than core either because

• they have dropped earlier support to deal with an issue - eg. extendededreports dropped Smarty2 support and omnimpay dropped php7.4 support OR
• they have not yet adapted to newer versions

Note that I think the fact that extension maintainers might need to make a one line update once a year is a feature, not a bug - as it helps people see what is maintained too.

ie I just added this to Omnipay

  <php_compatibility>
    <ver>8.0</ver>
    <ver>8.1</ver>
    <ver>8.2</ver>
    <ver>8.3</ver>
    <ver>8.4</ver>
  </php_compatibility>
  <smarty_compatibility>
    <ver>5</ver>
  </smarty_compatibility>