Web socket connection is not thread safe

[joffrey-bion]

It seems that interacting from several page sessions that were spawned by the same browser session (thus sharing the same web socket) is not thread safe.

We can run into this exception:

Send pending
java.lang.IllegalStateException: Send pending
	at java.net.http/jdk.internal.net.http.websocket.WebSocketImpl.sendText(WebSocketImpl.java:182)
	at org.hildan.krossbow.websocket.jdk.Jdk11WebSocketSession.sendText(Jdk11WebSocketClient.kt:105)
	at org.hildan.chrome.devtools.protocol.ChromeDPConnection.request(ChromeDPConnection.kt:27)
	at org.hildan.chrome.devtools.protocol.ChromeDPSession.request(ChromeDPSession.kt:39)
	at org.hildan.chrome.devtools.domains.target.TargetDomain.createBrowserContext(TargetDomain.kt:586)
	at org.hildan.chrome.devtools.targets.TargetExtensionsKt.attachToNewPage(TargetExtensions.kt:47)
	at org.hildan.chrome.devtools.targets.TargetExtensionsKt.attachToNewPage$default(TargetExtensions.kt:44)
	at IntegrationTests$test_parallelPages$1$invokeSuspend$$inlined$use$lambda$1.invokeSuspend(IntegrationTests.kt:103)

This is consistently reproduced by this test case:
https://github.com/joffrey-bion/chrome-devtools-kotlin/blob/main/src/test/kotlin/IntegrationTests.kt#L95