Instrumentation: Write cmakeInstall snippet on interrupted install

With instrumentation enabled, interrupting `cmake --install` (Ctrl+C)
terminated the process before its overall `cmakeInstall` envelope
snippet was written, orphaning the per-script `install` snippets.

Extend the `cmake --build` interrupt handling to the install site: wrap
the `cmakeInstall` command in `HandleInterrupt`, skip the post-install
hook, and re-raise so the exit status reflects the signal.  Add
cooperative cancellation so the command unwinds -- serial-loop and
parallel `queueScripts` guards stop launching further scripts, and the
parallel failure aggregation is scoped to dispatched runners so
un-launched scripts are not counted as failed.  Force a non-zero result
on interrupt (Windows cannot re-raise), and write the envelope
atomically so a second Ctrl+C cannot truncate it.

Issue: #27859