Regenerate CI workflows with xmsconan 2.16.0

[wdolinar]

Bumps the xmsconan pin to 2.16.0 (was 2.15.5).

Why this matters more than the diff suggests

The tracked change is five pin lines, but the effect is on the published artifact. xmsconan 2.16.0 compiles testing_sources into the library again, so a build produced under this pin publishes xmscore's testing helpers — ttEqualPointsXYZ, ttTextFilesEqual and friends — for dependent libraries to link.

CMakeLists.txt is generated at build time by the Generate Build Files step and is not tracked in this repo, so the pin is the entire change here. Regenerating locally with 2.16.0 confirms the rendered file now contains:

if (NOT IS_PYTHON_BUILD)
    list(APPEND xmscore_sources ${xmscore_testing_sources})
endif ()

Coverage.yaml moves to xmsconan>=2.16.0, keeping >= as the canary.

Context

xmscore 7.0.8 (2026-05-06) is the last release whose library carries the testing helpers — xmsconan 2.15.1 moved them into the runner target eight days later. 7.0.9 and 7.0.10 were therefore built without them, and downstream libraries fail to link against those builds:

undefined reference to `xms::ttTextFilesEqual(...)'

71 files across six repos depend on those symbols. This is the first half of the fix; the second is releasing xmscore so a package built under 2.16.0 actually exists on the remote.

Verification

flake8 --extend-ignore=AQU _package -> exit 0

The real verification is CI itself — particularly the Coverage workflow, which exercises the two-build split (testing=True+pybind=False and testing=False+pybind=True) that this change depends on for its safety argument.

To be released as 7.0.11, after which xmsgrid can re-point at it and the cascade can resume.