[UI] Get the namespace from the user info for run iFrame

When we support multiple users in the future, beyond admin and unauthenticated users, we will need to get the namespace from the user info for the Pipeline Run and View Experiments iFrame

mlx/dashboard/origin-mlx/src/App.tsx

Lines 69 to 70 in bbcf7e1

    
           // TODO: get namespace from user info, use fixed value: mlx for now 
        
           element.contentWindow.postMessage({type: 'namespace-selected', value: 'mlx'}, origin);

Originally posted by @ckadner in #252 (comment)

FYI @yhwang @Tomcli

and also the experiment view iFrame :-)

and maybe figure out if we can use just one iFrame for both of them. my guess is yes

	// TODO: get namespace from user info, use fixed value: mlx for now
	element.contentWindow.postMessage({type: 'namespace-selected', value: 'mlx'}, origin);