chore: migrate SFINAE to C++20 concepts for partitioner, extractor

[DennisOSRM]

Issue

Closes #7535

Replaces std::enable_if ownership-mode guards with C++20 trailing requires clauses in partitioner and extractor templates. Follows the same pattern already established in packed_vector.hpp and static_rtree.hpp.

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Tasklist

• self-review code for correctness and following the coding guidelines
• add tests (see testing)
• update relevant wiki pages
• review

Requirements / Relations

Part of #7530 (SFINAE → Concepts umbrella)
Related: #7632, #7631

Changes

• include/partitioner/multi_level_partition.hpp: 2 ownership-gated constructors → trailing requires
• include/partitioner/cell_storage.hpp: 2 constructors + GetCell() → trailing requires
• include/extractor/node_data_container.hpp: Renumber() → trailing requires

Build verified: all 77 targets compile cleanly.

[Copilot]

Pull request overview

Refactors ownership-mode gated overloads in partitioner and extractor templates by replacing std::enable_if-based SFINAE with C++20 trailing requires clauses. This aligns these modules with the concepts-based pattern already used elsewhere in the codebase and improves constraint readability/diagnostics without intended runtime behavior changes.

Changes:

• Replace ownership-gated constructors in MultiLevelPartitionImpl with trailing requires constraints.
• Replace ownership-gated constructors and GetCell() in CellStorageImpl with trailing requires constraints.
• Constrain EdgeBasedNodeDataContainerImpl::Renumber() with a trailing requires clause for container ownership only.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
include/partitioner/multi_level_partition.hpp	Converts container/view constructor gating from SFINAE to trailing requires constraints.
include/partitioner/cell_storage.hpp	Converts container/view constructors and container-only GetCell() from SFINAE to trailing requires constraints.
include/extractor/node_data_container.hpp	Converts container-only Renumber() gating from SFINAE to trailing requires constraint.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.22%. Comparing base (58fb6e6) to head (e974abc).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7637      +/-   ##
==========================================
+ Coverage   90.80%   94.22%   +3.41%     
==========================================
  Files         484      484              
  Lines       37789    37789              
==========================================
+ Hits        34316    35606    +1290     
+ Misses       3473     2183    -1290     

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