[4.x] Fix LDAP debugging functionality

[tatankat]

Pull Request for Issue mentioned in https://github.com/joomla/joomla-cms/pull/37959#issuecomment-1162373727

Summary of Changes

• Set ldap client log level to 7, using the symfony ldap client library.
• Require a newer LDAP symfony library, which includes a fix for "bug https://github.com/symfony/symfony/pull/46325 [Ldap] Fix LDAP connection options (@buffcode)" (see https://github.com/symfony/symfony/releases/tag/v5.4.9)

Testing Instructions

Toggle LDAP "Debug", do a login and check the error log for debug statements.

Actual result BEFORE applying this Pull Request

No effect when enabling LDAP "Debug".

Expected result AFTER applying this Pull Request

LDAP debug statements in the php error log.

Documentation Changes Required

none

Remark

Not included in one of my other LDAP PRs as this one includes a change to composer.json