ci: add ASan coverage for hook-built native assets

[HamdaanAliQuatil]

The upstream work needed to run hook-built native assets under sanitizer runtimes has landed:

• [dartdev] Add shared runtime for Linux CLI bundles dart-lang/sdk#63690 added shared Linux CLI runtimes.
• [test] Support CLI compiler for sanitizer runtimes dart-lang/test#2708 added dart test -c cli support for ASan, MSan, and TSan.
• [dartdev] Test CLI sanitizers with native assets dart-lang/sdk#63987 added end-to-end SDK coverage using a hook-built native asset.

The remaining release dependency is a published package:test version containing dart-lang/test#2708. The change is currently on package:test master under 1.32.0-wip, while the latest published version still predates it.

Once that version is available:

• add a Linux ASan CI lane using dart test -c cli -p vm-asan;
• exercise the existing FFI memory-pressure workload through the public API;
• share the workload with the existing Valgrind target rather than duplicating it;
• keep the Valgrind lane, since it provides complementary coverage;
• force native assets to build from source if packaged prebuilts are enabled, so the native code is sanitizer-instrumented.

ASan should be the first lane. MSan and TSan can follow once the ASan job is stable and their runtime behavior has been evaluated.