Make native CSS runtime tests portable to MSVC #846

Problem

The exact Windows native-runtime build reaches two deterministic portability errors after the preceding compiler stack:

• MSVC C2026 at native_v8_runtime_browser_dom_tests.inc: the stylesheet mutation setup is one oversized raw string literal;
• native_css_url_escape_oracle_tests.cpp includes <sys/resource.h> unconditionally, although RSS sampling is already optional on unsupported platforms.

The same run also showed one isolated Cannot open compiler generated file: Invalid argument for a small graphics contract target. The generated object path is 263 characters in the full parser/snapshot/graphics build variant, exceeding the classic Windows path boundary.

Fix

• partition the stylesheet mutation JavaScript source into bounded raw literal chunks joined at runtime;
• include and call getrusage only on Apple/Linux and return zero for unsupported peak-RSS sampling;
• shorten only the internal CMake target name while preserving its public CTest name and labels;
• keep script text, performance gates, and runtime behavior unchanged.

Acceptance

The exact win-x64 runtime target compiles past both files. Linux/macOS retain their RSS gates. The external-image contract target builds with an object path below 260 characters while its public test identity remains unchanged.