Update tests for sendTerminal operations when can check terminal updates

[bfitzpat]

While working on #46 we tried writing tests to ensure that the methods sendTerminalCtrlC and sendTerminalText are actually working properly. It turns out we don't have a clean way (beyond relying on "side effects" like creating a file via a command-line call and checking to see if the file is created) to simply watch for terminal output.

It appears that a new listener method is coming. @lhein found this https://stackoverflow.com/questions/57630371/how-to-use-terminal-api-to-listen-to-all-terminal-output-in-vscode which seems to be in the Insiders build. Once it appears in a public API form, maybe we can use it to watch for data changes in terminals.

When that occurs, we need to update the tests in the extensionFunctions.test.ts added by #47