make all experimental warning messages consistent

[pd4d10]

Some experimental warning messages' contents are not consistent, for example:

(node:70168) ExperimentalWarning: The ESM module loader is experimental.
(node:70372) ExperimentalWarning: Conditional exports is an experimental feature. This feature could change at any time

Shall we make them consistent? If so I'm willing to submit a PR to solve this.

There are two general methods to emit experimental warnings. I think we can make use of them.

JavaScript version

node/lib/internal/util.js

Lines 170 to 176 in 1549c8e

	function emitExperimentalWarning(feature) {
	if (experimentalWarnings.has(feature)) return;
	const msg = `${feature} is an experimental feature. This feature could ` +
	'change at any time';
	experimentalWarnings.add(feature);
	process.emitWarning(msg, 'ExperimentalWarning');
	}

C++ version (introduced in #30617)

node/src/node_process_events.cc

Lines 102 to 112 in 1549c8e

	Maybe<bool> ProcessEmitExperimentalWarning(Environment* env,
	const char* warning) {
	if (experimental_warnings.find(warning) != experimental_warnings.end())
	return Nothing<bool>();
	experimental_warnings.insert(warning);
	std::string message(warning);
	message.append(
	" is an experimental feature. This feature could change at any time");
	return ProcessEmitWarningGeneric(env, message.c_str(), "ExperimentalWarning");
	}

[pd4d10]

/cc @guybedford

[guybedford]

We've had the The ESM Loader is experimental message for long enough that I think this one is fine to leave as-is until we remove it.

If there are other inconsistencies though we should change them.

[pd4d10]

OK, get it. Found these flags. Seems not related to module.

(node:70168) ExperimentalWarning: Policies are experimental. # --experimental-policy
(node:70168) ExperimentalWarning: The --frozen-intrinsics flag is experimental # --frozen-intrinsics

[guybedford]

Those both seem worth doing to me. The added benefit is ensuring that the code examples follow the correct patterns for future reference.

[guybedford]

(//cc @bmeck)