Big regression in analysis phase in 1.1-rc1

[cgruber]

Something introduced between 1.0 and 1.1-rc1 results in much slower analysis phase, in particular, it seems to be during the parsing/merging of the poms. It's unclear why, since (it seems) like the same work is being done, just shifted in order, but it needs debugging.

This is a blocker to 1.1

[cgruber]

Now that github.com/square/maven-archeologist is out, we should just rip out the starlark xml parsing and use that. It can handle locally cached poms/artifacts, it can be used to create a parallel fetching strategy (starlark can't do that in repository_rules).

[cgruber]

This is obsolete with the 2.0 design changes, which don't use starlark xml handling.