minor symfony#61280 [DependencyInjection] Dump XML using plain PHP, no DOM needed (nicolas-grekas)

This PR was merged into the 7.4 branch.

Discussion
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[DependencyInjection] Dump XML using plain PHP, no DOM needed

| Q             | A
| ------------- | ---
| Branch?       | 7.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        | -
| License       | MIT

Sibling to symfony#60568

On the path to remove `ext-xml` from our minimum requirements.

See symfony#60568 (comment)

Commits
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6b04d14 [DependencyInjection] Dump XML using plain PHP, no DOM needed

Author: nicolas-grekas