Add API to track lsp perf on language client level

[testforstephen]

This PR provides an API to easily trace the lsp request performance.

• Track initialize request on languageClient.start()
• Track common requests on sendRequest(...)

Here is a sample code on how to use this API:

 const javaExt = vscode.extensions.getExtension("redhat.java");
 if (javaExt.exports.onDidRequestEnd) {
    javaExt.exports.onDidRequestEnd((traceEvent: any) => {
      console.log(`${traceEvent.type} - ${traceEvent.duration} ms - ${traceEvent.error}`);
    });
  }

[testforstephen]

// @akaroml @Eskibear @CsCherrYY pls help a review on the API design as well.

[jdneo]

Would be better to use performance.now(). See: https://developer.mozilla.org/en-US/docs/Web/API/Performance/now

Also, Date.now() may have been impacted by system and user clock adjustments, clock skew, etc. as it is relative to the Unix epoch (1970-01-01T00:00:00Z) and dependent on the system clock. The performance.now() method on the other hand is relative to the timeOrigin property which is a monotonic clock: its current time never decreases and isn't subject to adjustments.

[testforstephen]

thanks. Good to know the new API.

The data will like textDocument/completion - 1359.5962999993935 ms with performance.now api. Then the downstream tracer can decide whether to convert the floating point number to integer.

[jdneo]

LGTM