Parallelize analyze_srpm_buildroots in Content Resolver

[tdawson]

Parallelize the portion of Content Resolver that analyzes the srpm buildroots.
I believe this is going to raise the memory requirements higher than parallelizing the root log resolving. So it would be good to have it's own, separate max parallelizing variable, at least at first.

[tdawson]

I did a quick "AI Look at it", having it do the parrallelizing the same as the root logs.
The problem is the dnf lock.
You get a slight speedup. But because of the dnf lock only allows one thing to query at a time, the speedup is just the extra overhead around the dnf query.
Unless we can get multiple dnf queries going at the same time, this isn't worth the extra code and memory overhead.