Add fluegases heat loss component

[pierre-eliep-met]

Goal

⚠️ This PR is a duplicate of @hvernier's modifications not yet in a PR, probably better to wait then
Simply fixes #226

Type of change

• Bugfix (non-breaking change which fixes a bug/issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change which reorganizes code)
• Release & Version Update (when cumulative changes justify a release)
• Documentation Update

Checklist

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GitHub checks:

• I have added the appropriate tags, reviewers, projects and linked issues to this PR
• I have checked for conflicts with target branch, and merged/rebased in consequence

Model development checks:

• I have performed a self-review of my own code
• I have checked that my changes do not bring any retrocompatibility issue comparing to MML3-DTG-v3 version
• Existing tests pass (including Metroscopia !).
• I have added/updated tests that prove my development works and does not break anything.

Library checks:

• I have checked in the file explorer that I am not adding duplicate file/folder/package (due to renaming or moving file/package)
• I have checked that the packages I upload are stored as separate files

Documentation checks:

• I have made corresponding changes or additions to the documentation
• I have added corresponding entries to the Changelog

[pierre-eliep-met]

⚠️ This PR is a duplicate of @hvernier's modifications not yet in a PR, probably better to wait then