Exclude Set instance methods from polyfills (WordPress#67230)

* Exclude Set instance methods from polyfills

* Switch to regexp exclusions

packages/babel-preset-default/polyfill-exclusions.js

@@ -7,4 +7,25 @@ module.exports = [
 	// This is an IE-only feature which we don't use, and don't want to polyfill.
 	// @see https://github.com/WordPress/gutenberg/pull/49234
 	'web.immediate',
+	// Remove Set feature polyfills.
+	//
+	// The Babel/core-js integration has a severe limitation, in that any Set
+	// objects (e.g. `new Set()`) are assumed to need all instance methods, and
+	// get them all polyfilled. There is no validation as to whether those
+	// methods are actually in use.
+	//
+	// This limitation causes a number of packages to unnecessarily get a
+	// dependency on `wp-polyfill`, which in most cases gets loaded as part of
+	// the critical path and can thus have an impact on performance.
+	//
+	// There is no good solution to this, and the one we've opted for here is
+	// to disable polyfilling these features entirely. Developers will need to
+	// take care not to use them in scenarios where the code may be running in
+	// older browsers without native support for them.
+	//
+	// These need to be specified as both `es.` and `esnext.` due to the way
+	// internal dependencies are set up in Babel / core-js.
+	//
+	// @see https://github.com/WordPress/gutenberg/pull/67230
+	/^es(next)?\.set\./,
 ];