Run more tests in the browser

[albrow]

There are some tests which we currently don't run in the browser (they are excluded by build tags) but should be able to. For example, look at the orderwatch package. It looks like one reason for this is that wasmbrowsertest doesn't support the --serial flag. To workaround this we could potentially use an environment variable instead of a flag. Another reason for this historically has been the inability to declare certain globals that Mesh depends on in the browser. However, as of #811 we have a way to do this.