refactor: remove dependency on boost.tti using detector idiom

[Becheler]

Remove dependency to Boost.TTI. Use void_t detector idiom instead.

Before submitting

• This PR targets the develop branch.
• I searched for an existing PR or issue covering the same change.
• My contribution is licensed under the Boost Software License 1.0.

Type of change

• Bug fix
• New feature or API addition
• Refactor (no behavior change)
• Documentation
• Build, CI, or tooling
• Other (specify below)

Does this PR introduce a breaking change?

• Yes (describe migration impact below)
• No

What this PR does

Removes Boost.Graph's dependency on Boost.TTI (and the last MPL use in DFS).

• depth_first_search.hpp: replaced the BOOST_TTI_HAS_MEMBER_FUNCTION(finish_edge) detector and its __GNUC__/clang/intel #if fork with a void_t expression-SFINAE detector, has_finish_edge<Vis, E, G>, that checks whether vis.finish_edge(e, g) is a valid call. D
• dropped #include <boost/tti/has_member_function.hpp>
• added <boost/type_traits/make_void.hpp> and <type_traits>.
• This also removes the mpl::vector<E, const G&> that only existed to feed TTI's signature, so the file is now MPL-free as well.
• build.jam: dropped /boost/tti//boost_tti.
• CMakeLists.txt: dropped Boost::tti.

All changes in boost::detail, detection is identical for void finish_edge(Edge, const Graph&) visitors, and the check now works uniformly on C++14 compilers.

Motivation

It's not worth pulling a Boost dependency anymore now that the sfinae + detector idiom are available in C++14.

Testing

Checklist

• Existing tests pass (b2 in the test/ directory).
• New behavior is covered by a test, or this is a docs / build / refactor change.
• Documentation was updated if user-facing behavior changed.
• No new compiler warnings on the platforms I built against.

[github-actions]

Compiler-warning counts vs develop (auto-generated).
PR run 29568558245 vs develop run 29503421610 (b3cb64738b).

Job	Baseline	After	Delta
macos (clang, 14)	4	4	0
macos (clang, 17)	4	4	0
macos (clang, 20)	4	4	0
ubuntu (clang-19, 14)	4	4	0
ubuntu (clang-19, 17)	4	4	0
ubuntu (clang-19, 20)	4	4	0
ubuntu (clang-19, 23)	4	4	0
ubuntu (gcc-14, 14)	10	10	0
ubuntu (gcc-14, 17)	10	10	0
ubuntu (gcc-14, 20)	10	10	0
ubuntu (gcc-14, 23)	10	10	0
windows_msvc_14_3 (msvc-14.3)	971	971	0

[github-actions]

Boost dependency footprint vs develop (auto-generated).
PR run 29568558172 vs develop run 29503421582 (b3cb64738b).

Header-inclusion weights (graph files pulling each direct dependency in):

Dependency	develop	PR	Δ
tti	1	0	-1
type_traits	40	41	+1

Transitive Boost modules: 69 → 68 (-1)

• removed: tti