Custom devserver implementation

[dgp1130]

Currently we use concatjs_devserver() as the implementation of the web_resources_devserver(). This is nice to not have to write a devserver and because it is ibazel compatible and implements livereload out of the box.

However, with v3 moving this to @bazel/concatjs, which includes Karma rules and requires a dependency on rules_webtesting, this is a very heavyweight dependency that gets passed to user projects and which we only use a small portion of. Using a custom devserver would enable user workspaces to drop @bazel/concatjs and rules_webtesting.

[dgp1130]

Happened upon live-server the other day, which has a PR open to add iBazel support. Maybe this could be used as an out of the box devserver?

[dgp1130]

We're now using http-server for web_resources_devserver(). I'll need to look into live reload, but it should already be iBazel-compatible.