[23150] Apply user template to included IDL files (backport #472)

[mergify]

Description

This PR is backport of #472:
This PR adds the required logic to apply user templates to included IDL files.
If the output file name specified in -extrastg contains the character '@', the custom template will be also applied to included IDL files. The '@' will be replaced with the included file name.

Usage example:
-extrastg /path/to/template/Custom.stg @MyCustomTemplate.cpp

Above command will generate file: HelloWorldMyCustomTemplate.cpp in case HelloWorld.idl was included.

@Mergifyio backport 3.3.x 2.5.x

Contributor Checklist

• Commit messages follow the project guidelines.

• Tests that thoroughly check the new feature have been added/Regression tests checking the bug and its fix have been added; the added tests pass locally

• New feature has been documented/Current behavior is correctly described in the documentation.

• 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.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.

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This is an automatic backport of pull request #474 done by [Mergify](https://mergify.com).

[mergify]

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	both modified:   src/main/java/com/eprosima/fastdds/fastddsgen.java

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