main gained risk-control host signals, which changed the cachedHttpClientFunc
and cachedLarkClientFunc signatures and rewrote the proxy-warning test around
TestFactory. The only conflict was that test's import block: this branch moved
the shared environment variable names out of internal/envvars into envnames,
while main still imported the old package.
Keep envnames for the five constants that moved and add internal/core for the
config types the rewritten test now builds. internal/envvars is no longer
needed here; its remaining constants are the internal-only ones.
e5b2e96df4