[5.x] Consider removing `strict_types`

[cleptric]

We might be able to create a more robust SDK by removing declare(strict_types=1) from the code base. While we would need to be more cautions about type coercion, we would throw no more TypeErrors.
Let's investigate and document it.
Make sure to add the commit to https://github.com/getsentry/sentry-php/blob/master/.git-blame-ignore-revs after merging.

[linear]

PHP-27 Consider removing `strict_types`