ci: run the compiler PHPT suite under UBSan

[Giandonn]

The compiler rejects every statically detectable undefined operation, but undefined behavior that only shows up at runtime in the generated C++ is compiled into whatever the CPU happens to do. tpc already supports --sanitize, but nothing in CI used it, so a regression of this kind is invisible to the test suite: the binary prints some value, and if the PHPT expectation was written from that binary, the test passes.

The change

• run-tests.php --sanitize <list> (undefined, address, or both): every test binary is compiled with --sanitize <list>, and UBSAN_OPTIONS=halt_on_error=1 turns a report into a failing test instead of a line in its output. The option reaches the parallel workers together with the other globals. An unknown sanitizer is rejected up front.
• The Linux PHPT job gets one extra matrix entry, PHP 8.5 with sanitize: undefined. sanitize: [""] in the base matrix makes GitHub add it as a separate job rather than merging the key into the existing PHP 8.5 entry. Its artifacts get a -undefined suffix, and release packaging still comes only from the unsanitized entries.

It catches what it should

A PHPT whose expectation was written from the binary (shiftLeft(1, 64) prints 1) passes without the option and fails with it, with the location in the generated C++:

$ php run-tests.php tmp/ub-shift.phpt                       -> PASS
$ php run-tests.php --sanitize undefined tmp/ub-shift.phpt  -> FAIL
ub-shift.cc:21:34: runtime error: shift exponent 64 is too large for 64-bit type 'long int'

The same trap fails when it runs among other tests with -j4, so the option does reach the workers and is not bypassed by the build cache (sanitize is part of the native command options).

The current suite is clean

	PHPT tests/compiler with --sanitize undefined
Local, PHP 8.4.26 ZTS, GCC 11	1247 passed, 0 failed, 27 skipped
This branch on GitHub Actions (PHPT - PHP 8.5 ZTS (undefined sanitizer))	1272 passed, 0 failed, 2 skipped

So the job starts green; from here on, new undefined behavior in generated code fails CI instead of silently changing results. All 9 jobs of that run passed, and actionlint reports no issues for the workflow.