Move build to worker

[soapy1]

Building should only be done by workers. Other pieces of the application should not be accessing this module.

Pull request checklist

• Did you test this change locally?
• Did you update the documentation (if required)?
• Did you add/update relevant tests for this change (if required)?

Additional information

Previously, the coverage for build.py

conda_store_server/_internal/build.py         175     47    73%

Marginally increases

conda_store_server/_internal/worker/build.py      175     43    75%

[netlify]

✅ Deploy Preview for conda-store canceled.

Name	Link
🔨 Latest commit	bd50adc
🔍 Latest deploy log	https://app.netlify.com/sites/conda-store/deploys/6723f9d279b783000856e9c0

[netlify]

✅ Deploy Preview for conda-store canceled.

Name	Link
🔨 Latest commit	471ceb7
🔍 Latest deploy log	https://app.netlify.com/sites/conda-store/deploys/67253b38694bee0008f72e58

[peytondmurray]

I like the reorganization. I can see why this stuff wasn't tested before (it just sets values on Build items in the database in a pretty minimal way), but it's definitely good to have a more robust test suite here.