Add compatibility with composer v2.4+

[stefangr]

When running the dependabot-script with DEBUG_HELPERS=true I saw this error:

PHP Deprecated:  Installer::setIgnorePlatformRequirements is deprecated since Composer 2.2, use setPlatformRequirementFilter instead. in /opt/composer/v2/vendor/composer/composer/src/Composer/Installer.php on line 1289

In this PR I work around the deprecations (there was one more, which was not verbose) and also added a forward compatible change to disable the audit.

Applied changes:

• Use eventDispatcher::setRunScripts instead of deprecated Installer::setRunScripts
• Use Installer::setPlatformRequirementFilter instead of deprecated Installer::setIgnorePlatformRequirements
• Use setAudit(false) if Installer has that method

[jeffwidman]

Oh perfect timing, I was planning to work on #5720 / #6385 / #6385 (comment) later this week!

I suspect life is simpler if we just keep on the latest composer and don't worry about backwards compatibility for options... I assume most folks run dependabot within the context of our bundled dependabot-core image, so they'll be using whatever version of composer is bundled with that. If you think differently for some reason, please let me know.

For simplicity of working across timezones / PR rebases, does the following sound reasonable?

1. Merge this
2. Rebase the Dependabot PR to bump composer to 2.5.x
3. Add a commit remove the optional checks, such that setAudit is always called.
4. Merge... so hopefully we'll be back up to composer latest by EOD 👍

[jeffwidman]

😍 for fixing this, as a non-PHP expert, I would have muddled for a while before realizing it needed another import...

[stefangr]

For simplicity of working across timezones / PR rebases, does the following sound reasonable?

1. Merge this

2. Rebase the Dependabot PR to bump `composer` to `2.5.x`

3. Add a commit remove the optional checks, such that `setAudit` is always called.

4. Merge... so hopefully we'll be back up to `composer` `latest` by EOD +1

That sounds completely reasonable. 👍