Timeout when auto-starting trace server, with url ending with a slash

[marcdumais-work]

The trace server URL is configured as a preference, contributed in the vscode-trace-extension:

For the end-user it may not seem unreasonable to add a slash at the end of the URL, but when that is done, it results in a timeout, when attempting to start the trace server. This is because we currently add another slash, when resolving the complete TSP API URL, as part of the health-check that confirm the server was succeessfully started:

It would be easy enough to check for the presence of the slash at the end of the server URL, and not add a second onie if already present, as it's done in the trace viewer: