fix(core): install global polyfills only when missing, without materializing lazy runtime globals - #11360

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What is the current behavior?

• registerOnGlobalContext (the lazy CJS install path) checks for an existing global with a property read (if (global[exportName])). On runtimes that expose lazy self-installing globals (e.g. TextDecoder), that read forces the native implementation to materialize eagerly, defeating the runtime's laziness. Truthiness also means a defined-but-falsy global would get shadowed.
• installPolyfills (eager ESM/snapshot path) loads the polyfill module even when the runtime already provides every requested export.
• global.crypto is overwritten unconditionally, clobbering a runtime-provided crypto.

What is the new behavior?

Polyfills are installed only when the corresponding global is actually missing, and presence is always checked with the in operator, which does a HasProperty lookup without invoking getters or lazy-property callbacks — so checking for TextDecoder no longer evaluates it. (Object.getOwnPropertyDescriptor would not be safe here either: V8 resolves lazy data properties to produce the descriptor.)

• installPolyfills filters the export list down to names missing from global first, and skips loading the polyfill module entirely when the runtime provides everything.
• registerOnGlobalContext bails out via exportName in global instead of reading the property.
• global.crypto is only assigned when absent.