Improve debugging via Vardumper overriding #19308

Description:

Fixes regression of https://github.com/matomo-org/matomo/issues/6890
Same as https://github.com/matomo-org/matomo/commit/6130e7e86baff2979bb84bf979a13130124c1202

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed

Hi,

Can you maybe explain a bit more why this change is needed? The linked PR and commit are nearly a decade old and we are currently more in the process of removing upgradephp (https://github.com/matomo-org/matomo/pull/16650)

@Findus23 currently dump() does nothing because it is defined as empty function in libs/upgradephp/upgrade.php. That definition must come after original var-dumper autoloading (via require_once PIWIK_VENDOR_PATH . '/autoload.php';)

@Findus23 we could move it in other place but I'm not sure where it should be