servlet: Ignore timeoutOnSleepingServer for Tomcat (1.77.x backport)

[ejona86]

tomcat10Test is frequently failing on Windows because Tomcat doesn't support trailers-only. I removed the FIXMEs because we won't workaround Tomcat in grpc-servlet because:

1. An interceptor that converts trailers-only into headers+trailers would handle most cases, as it could run directly next to the application. That is semantically very safe. But an interceptor doesn't help deadline handling and other transport-caused closures, as those trailers-only are produced by the transport
2. Having the transport convert trailers-only would work for deadline handling, but is not semantically safe
3. The other languages didn't find Tomcat to be important enough to support HEADERS+empty DATA(END_STREAM) as trailers-only on the client-side

Unexpected status: Status{code=INTERNAL, description=Received unexpected EOS on empty DATA frame from server, cause=null}
value of: getCode()
expected: DEADLINE_EXCEEDED
but was : INTERNAL
	at app//io.grpc.testing.integration.AbstractInteropTest.assertCodeEquals(AbstractInteropTest.java:2028)
	at app//io.grpc.testing.integration.AbstractInteropTest.timeoutOnSleepingServer(AbstractInteropTest.java:1644)

Backport of #12510