[21655] Add default subscriber profile in ROS 2 XML configuration (backport #910)

[mergify]

Description

This PR adds the default subscriber profile in ROS 2 XML configuration snippet. This is particularly interesting for 2.6.x as if the default profile defaults readers historymemroypolicy to PREALLOCATED.

@Mergifyio backport 2.14.x 2.10.x 2.6.x

Contributor Checklist

• Commit messages follow the project guidelines.
• Code snippets related to the added documentation have been provided.
• Documentation tests pass locally.
• Applicable backports have been included in the description.

Reviewer Checklist

• The PR has a milestone assigned.
• The title and description correctly express the PR's purpose.
• Check contributor checklist is correct.
• CI passes without warnings or errors.

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This is an automatic backport of pull request #910 done by [Mergify](https://mergify.com).