Consolidate optimize.sh and optimize_workspace.sh

[webmaster128]

Follow-up on #134. Once we have the same calling convention for bob in optimize.sh and optimize_workspace.sh, we can use the same docker image for single contract builds as well as workspaces. This is nice and convenient for everyone.

Looking at the diff, there are the following tasks:

• [x] Remove sccache from rust-optimizer (#137)
• [x] Remove multi argument (multi sontract) support from rust-optimizer (https://github.com/CosmWasm/rust-optimizer/pull/138)
• [x] Remove INTERMEDIATE debugging (https://github.com/CosmWasm/rust-optimizer/pull/140)