fix: teach cmake install-test to use Boost::headers for B2 installs

[Becheler]

• B2 does not install a per-library CMake config for header-only libraries, so consume the generic Boost::headers target and alias it to keep the target name consistent with the CMake installed case.
• Fixed the intentional memory leak that was failing CI since the test/suppressions.txt support through LSAN_OPTIONS was silently dropped when migrating to boost ci in 2025.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.06%. Comparing base (e50f160) to head (3629aac).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop      #39   +/-   ##
========================================
  Coverage    92.06%   92.06%           
========================================
  Files            5        5           
  Lines          126      126           
  Branches        47       47           
========================================
  Hits           116      116           
  Misses           6        6           
  Partials         4        4           

---

Continue to review full report in Codecov by Harness.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e50f160...3629aac. Read the comment docs.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[pdimov]

The first change shouldn't be necessary any longer.

[pdimov]

But you still need to change find_package(boost_property_map REQUIRED) to find_package(Boost REQUIRED COMPONENTS property_map).