[25469] Improve generated header guards (backport #587)

[mergify]

Description

• Header guards should not include characters other than capital letters, numbers, and underscores.
• IDL files with the same name in different folders should have different header guards
• For the use case of separate invocations of fastddsgen from different folders, where two different IDL files could have the same relative path, take into account the namespace of the last declared structure, or the namespace of the last declaration.

@Mergifyio backport 4.0.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

• N/A: 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.

---

This is an automatic backport of pull request #587 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 72f89a0 has failed:

On branch mergify/bp/4.0.x/pr-587
Your branch is up to date with 'origin/4.0.x'.

You are currently cherry-picking commit 72f89a0.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   src/test/java/com/eprosima/fastdds/FastDDSGenTest.java

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   src/main/java/com/eprosima/fastdds/idl/grammar/Context.java

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[mergify]

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