[21185] Examples refactor: Flow Controller

[elianalf]

Description

This PR is part of a suite of PR which would make a refactor in the repository examples.
It is intended to apply to most of the examples, by making them homogeneous, more understandable, and more specific to the case they were meant to be.

In this Flow Controller example, the key changes are:

• The publishers continuously send samples. The user can set the number of samples to send.
• The user can set the following Qos and Properties for the Flow Controller:
  • Scheduler policy used by the flow controller.
  • Maximum number of bytes to be sent to network per period.
  • Period of time in milliseconds on which the flow controller is allowed to send the maximum number of bytes per period.
  • Property fastdds.sfc.priority.
  • Property fastdds.sfc.bandwidth_reservation.

Contributor Checklist

• Commit messages follow the project guidelines.
• The code follows the style guidelines of this project.
• 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
• Any new/modified methods have been properly documented using Doxygen.
• N/A Any new configuration API has an equivalent XML API (with the corresponding XSD extension)
• N/A Changes are backport compatible: they do NOT break ABI nor change library core behavior.
• N/A Changes are API compatible.
• New feature has been added to the versions.md file (if applicable).
• N/A New feature has been documented/Current behavior is correctly described in the documentation.
• N/A 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.
• N/A: If this is a critical bug fix, backports to the critical-only supported branches have been requested.
• Check CI results: changes do not issue any warning.
• Check CI results: failing tests are unrelated with the changes.