Update environment checks

[JillieBeanSim]

our current istheia test can provide a false positive

for determining whether we're running in VSCode versus Theia, can use vscode.env.uriScheme instead of vscode.env.appName. 'uriScheme' seems to provide a somewhat simpler string to compare against

export function isVSCode(): boolean {
return (vscode.env.uriScheme == 'vscode' || vscode.env.uriScheme == 'vscodium');
}
export function isTheia(): boolean {
return (vscode.env.uriScheme == 'theia');
}