Revert "Unbundle Requests and urllib3; bump Requests to 2.2.1"

This reverts commit 0a4b2aa7c2a4870c6af91c59c19c7f48b83bb7f2.
Remove support for obsolete --no-{build,upload}-step flags.

These were undocumented flags for the exclusive use of the builder apps.
All dx-toolkit newer than 4fa2deb (v0.42.0, March 2013) will invoke the
builder apps such that those flags are not supplied to dx_build_app, and
the builder apps ceased to be able to supply these flags entirely in
dnanexus/dx_app_builder@4803fbba (tarball_app{,let}_builder versions
1.0.12 and higher).