ci(build-depends.repos): separate repos for humble and nightly

[xmfcx]

Description

Related Issue:

• Autoware stable compilation fails on main branch autoware#5792

Humble counterpart:

• ci(build-depends.repos): separate repos for humble and nightly #10146
• Included in chore(motion_velocity_planner_universe): fix build depends (#10122) #10139

build_depends.repos file is used for pulling the dependencies of this repository while building it, currently used by CI.

With the introduction of autoware-nightly.repos and pinning of the versions in autoware.repos, the management of this file became a bit complicated.

This repository has 2 branches: main and humble. This PR introduces the following configuration for both these:

PRs against main branch & CI that operates on main

They should utilize build_depends_humble.repos that is overridden by build_depends_nightly.repos.

To simplify this, I've added a new action that will overlay one .repos file onto another.

Using this new combine-repos-action these CI workflows now use the overlaid .repos file.

The reason for not having 2 .build_depends.repos files with some duplicate information and going with override option is to simplify version maintenance.

PRs against humble branch

These utilize build_depends_humble.repos as it is. The condition for this case is only triggered by *-differential workflows.

How was this PR tested?

• build-and-test-daily: https://github.com/autowarefoundation/autoware.universe/actions/runs/13384761188
• check-build-depends: https://github.com/autowarefoundation/autoware.universe/actions/runs/13384698882/job/37379204369?pr=10148

[mitsudome-r]

LGTM. We can merge it once we confirm that https://github.com/autowarefoundation/autoware.universe/actions/runs/13384761188/job/37379350785 passes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 26.76%. Comparing base (b4d9155) to head (2e895aa).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10148      +/-   ##
==========================================
- Coverage   26.76%   26.76%   -0.01%     
==========================================
  Files        1416     1416              
  Lines      108463   108463              
  Branches    41715    41715              
==========================================
- Hits        29033    29031       -2     
- Misses      76554    76556       +2     
  Partials     2876     2876              

Flag	Coverage Δ
total	26.76% <ø> (-0.01%)	⬇️

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