Migrate off boa / conda-mambabuild

[jakirkham]

Upstream has archived the boa repo, which supplies conda-mambuild that we use

We should migrate usages of conda-mambuild to either conda-build or rattler-build

The former may help us drop boa more efficiently

The latter is already in the works: #47

Filing to track this cleanup work

[vyasr]

Unless we're worried that existing boa binaries are going to disappear, given that we've already started on #47 and are targeting it for this release I see no real reason to spend time switching to conda-build.

[jakirkham]

My concern is it is pinning old versions of dependencies and not being updated

Dropping it simply lightens our load

We can do so for almost free (as replacing conda mambabuild with conda build uses the same solver with the same behavior)

[vyasr]

Got it, then sure go for it.