fix(ext/node): don't throw error on invalid path input on exists and existsSync (#29971)

Currently `fs.exists` and `fs.existsSync` throws error when invalid path
is given to the input.

The expected behavior is to:
- Call the callback with false on `fs.exists`.
- Return false on `fs.existsSync`.

Towards #29972, #24236

ext/node/polyfills/internal/util.mjs

@@ -46,7 +46,9 @@ export function once(callback) {
 // In addition to being accessible through util.promisify.custom,
 // this symbol is registered globally and can be accessed in any environment as
 // Symbol.for('nodejs.util.promisify.custom').
-const kCustomPromisifiedSymbol = SymbolFor("nodejs.util.promisify.custom");
+export const kCustomPromisifiedSymbol = SymbolFor(
+  "nodejs.util.promisify.custom",
+);
 // This is an internal Node symbol used by functions returning multiple
 // arguments, e.g. ['bytesRead', 'buffer'] for fs.read().
 const kCustomPromisifyArgsSymbol = SymbolFor(