[chore] Provide consistent compatibility guidance for signals

[thompson-tomo]

Changes

When a signal type ie profile. trace have compatibility guidance, this is now captured under the common h2 heading with h3 headings for each specific mapping that has been defined.

This also ensures a consistent h1 pattern is used.

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Merge requirement checklist

• [x] CONTRIBUTING.md guidelines followed.
• [ ] Change log entry added, according to the guidelines in When to add a changelog entry.
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• [ ] Links to the prototypes or existing instrumentations (when adding or changing conventions)