Fixed structure of the Upgrading Project guide

[dubewarsagar]

What changes are you introducing?

• Created a new assembly and added Upgrading RH Satellite module into a new assembly.
• Moved the upgrade-related modules under the new assembly structure.
• Updated module inclusions to use the assembly hierarchy instead of relying on leveloffset=+2.

Why are you introducing these changes? (Explanation, links to references, issues, etc.)

Anything else to add? (Considerations, potential downsides, alternative solutions you have explored, etc.)

• The previous structure relied on leveloffset=+2 to maintain the document hierarchy. Converting the upgrade content into an assembly provides a more modular and maintainable structure that aligns with modular documentation practices.
• The new structure establishes a clear parent-child relationship between the upgrade content and its associated modules, improving content organization and reducing dependence on level offsets.

Contributor checklists

• The content itself remains unchanged; only the document structure has been reorganized.

• This change simplifies future maintenance by making the hierarchy explicit in the assembly rather than through include-time level adjustments.

• I am okay with my commits getting squashed when you merge this PR.

• I am familiar with the contributing guidelines.

Please cherry-pick my commits into:

• Foreman 3.19/Katello 4.21
• Foreman 3.18/Katello 4.20 (Satellite 6.19)
• Foreman 3.17/Katello 4.19
• Foreman 3.16/Katello 4.18 (Satellite 6.18; orcharhino 7.6, 7.7, and 7.8)
• Foreman 3.15/Katello 4.17
• Foreman 3.14/Katello 4.16 (Satellite 6.17; orcharhino 7.4; orcharhino 7.5)
• Foreman 3.13/Katello 4.15 (EL9 only)
• Foreman 3.12/Katello 4.14 (Satellite 6.16; orcharhino 7.2 on EL9 only; orcharhino 7.3)
• We do not accept PRs for Foreman older than 3.12.

[github-actions]

The PR preview for bd83d81 is available at theforeman-foreman-documentation-preview-pr-4915.surge.sh

No diff compared to the current base

show diff

[dubewarsagar]

Apply suggestions from the review.

[aneta-petrova]

Merged to "master" and cherry-picked:

f988e0f..4f238cc 3.19 -> 3.19
5df3d84..f643f1b 3.18 -> 3.18

There are conflicts on 3.17 but I think it's fine not to cherry-pick further since this is a no-diff change.