add intl extension to php images

[tobybellwood]

This PR adds the intl extension to the php8-based images (php7.4 is shortly to end support)

Closes #628

[tobybellwood]

confirmed present in images:

~/sites/lagoon-images  $ docker run --rm -it testlagoon/php-8.0-cli:pr-629 php -m | grep intl
intl
~/sites/lagoon-images  $ docker run --rm -it testlagoon/php-8.1-fpm:pr-629 php -m | grep intl
intl

[bomoko]

phpinfo is good

intl

Internationalization support => enabled
ICU version => 71.1
ICU Data version => 71.1
ICU Unicode version => 14.0

Directive => Local Value => Master Value
intl.default_locale => no value => no value
intl.error_level => 0 => 0
intl.use_exceptions => Off => Off

Let's merge