Unnecessary pop-ups following multiple language server failures.

[hopehadfield]

Upon five language server failures, up to five error messages appear, including the following:

"The Language Support for Java server crashed 5 times in the last 3 minutes. The server will not be restarted."
"Language Support for Java client: couldn't create connection to server."
"Connection to server got closed. Server will not be restarted."
"Language Support for Java (Syntax Server) client: couldn't create connection to server."
"Restarting server failed"

Looking to suppress some of the messages as the current amount is overkill.

[rgrunber]

For those interested, the key here was finding that the ClientErrorHandler's error() and closed() callbacks return a CloseHandlerResult/ErrorHandlerResult. They take an optional handled boolean field : https://github.com/microsoft/vscode-languageserver-node/blob/release/client/8.1.0/client/src/common/client.ts#L159-L165 :

/**
* If set to true the client assumes that the corresponding
* close handler has presented an appropriate message to the
* user and the message will only be log to the client's
* output channel.
*/
handled?: boolean;

So setting that to true should suppress the additional popups in quite a few cases. Note that his handles errors/closes after the connection has been established and not those in the process of establishing a connection (that gets handled by InitializationFailedHandler which we've addressed in https://github.com/redhat-developer/vscode-java/pull/3123/files#diff-04bba6a35cad1c794cbbe677678a51de13441b7a6ee8592b7b50be1f05c6f626L243-L246.