Refactor the Gitpod Server Launcher [Follow-up from #11232]

[felladrin]

To fix the issue about JetBrains IDEs not signaling heartbeats, we've brought back code from a previous implementation. Now that we confirmed the problem is fixed, we need to refactor the solution to avoid duplicated code and ensure it's covering all connection cases.

Also, we need to make backend-plugin work the same way as gateway-plugin regarding proxies. See below:

gitpod/components/ide/jetbrains/backend-plugin/src/main/kotlin/io/gitpod/jetbrains/remote/GitpodManager.kt

Lines 276 to 282 in aafcaf1

	launcher.listen(
	info.gitpodApi.endpoint,
	info.gitpodHost,
	plugin.pluginId.idString,
	plugin.version,
	tokenResponse.token
	)

gitpod/components/ide/jetbrains/gateway-plugin/src/main/kotlin/io/gitpod/jetbrains/gateway/GitpodConnectionService.kt

Lines 52 to 67 in aafcaf1

	val origin = "https://$gitpodHost/"
	val proxies = CommonProxy.getInstance().select(URL(origin))
	val sslContext = CertificateManager.getInstance().sslContext
	// see https://intellij-support.jetbrains.com/hc/en-us/community/posts/360003146180/comments/360000376240
	Thread.currentThread().contextClassLoader = GitpodConnectionProvider::class.java.classLoader
	launcher.listen(
	"wss://$gitpodHost/api/v1",
	origin,
	plugin.pluginId.idString,
	plugin.version,
	accessToken,
	proxies,
	sslContext
	)