Refreshing via ContextRefresher pins virtual threads

Describe the bug
With virtual threads enabled a call to /actuator/refresh pins virtual threads.

The ContextRefresher uses synchronized on both refresh and refreshEnvironment, so it seems they are not ready for use with virtual threads:

	public synchronized Set<String> refresh() {
		Set<String> keys = refreshEnvironment();
		this.scope.refreshAll();
		return keys;
	}

	public synchronized Set<String> refreshEnvironment() {
		Map<String, Object> before = extract(this.context.getEnvironment().getPropertySources());
		updateEnvironment();
		Set<String> keys = changes(before, extract(this.context.getEnvironment().getPropertySources())).keySet();
		this.context.publishEvent(new EnvironmentChangeEvent(this.context, keys));
		return keys;
	}

There could be more places of course

Are there plans to support virtual threads (with ReentrantLock)?

Start with ContextRefresher.refresh and refreshEnvironment, then inspect the surrounding refresh flow for other synchronized sections. Reproduce the /actuator/refresh path with virtual threads and compare the locking behavior; done means refresh operations no longer pin virtual threads while preserving safe concurrent environment and scope refreshes.