Switch nav2_smac_planner to modern CMake idioms.

[clalancette]

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Basic Info

Info	Please fill out this column
Ticket(s) this addresses	Follow-up to #4357
Primary OS tested on	Ubuntu 24.04
Robotic platform tested on	N/A
Does this PR contain AI generated software?	No

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Description of contribution in a few bullet points

Switch nav2_smac_planner to use modern CMake idioms:

1. Switch from ament_target_dependencies to target_link_libraries
2. Don't compile the common files in this package more than once. Instead, compile those into a library, then link that library into all of the other ones.
3. Export a CMake target so downstream packages can use it.
4. Push the include directories down one level, which is best practice since Humble.

Description of documentation updates required from your changes

None needed.

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Future work that may be required in bullet points

This is part of a larger series to switch Navigation2 to modern CMake idioms. After this PR, there 3 PRs to go.

For Maintainers:

• Check that any new parameters added are updated in docs.nav2.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists

[SteveMacenski]

nav2_package()?

[clalancette]

Good point.

When I turn that on locally, I get a host of new compiler warnings (which are then errors, because of -Werror). Would you like me to submit a separate PR where we only turn on nav2_package() and fix the warnings, or do you want me to just fix them all in this PR?

[SteveMacenski]

A new PR would be fine. Also, if you'd prefer, you could file a ticket with those errors and we can kick that can for another time entirely. I don't think that's critically in your path of what you're aiming to do, so I don't want to pile on - unless you'd like to :-)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files	Coverage Δ
..._smac_planner/include/nav2_smac_planner/a_star.hpp	50.00% <ø> (ø)
...r/include/nav2_smac_planner/analytic_expansion.hpp	100.00% <ø> (ø)
...smac_planner/include/nav2_smac_planner/node_2d.hpp	100.00% <ø> (ø)
...c_planner/include/nav2_smac_planner/node_basic.hpp	100.00% <ø> (ø)
..._planner/include/nav2_smac_planner/node_hybrid.hpp	95.83% <ø> (ø)
...planner/include/nav2_smac_planner/node_lattice.hpp	100.00% <ø> (ø)
...mac_planner/include/nav2_smac_planner/smoother.hpp	100.00% <ø> (ø)
...2_smac_planner/include/nav2_smac_planner/utils.hpp	98.64% <ø> (ø)
nav2_smac_planner/src/node_lattice.cpp	89.20% <ø> (ø)
nav2_smac_planner/src/smac_planner_hybrid.cpp	86.61% <ø> (ø)
... and 2 more

... and 2 files with indirect coverage changes