[docker] add local run for validator dynamic
[docker] add local run for validator dynamic

Now we can support running an arbitrary number of nodes locally in
docker. This helps facilitate test development rather than immediately
jumping into cluster-test, etc.

Usage:
install docker
build dynamic validator:
  cd libra && \
    ./docker/validator/build.sh && \
    ./docker/validator-dynamic/build-dynamic.sh
run the dynamic validator:
./docker/validator-dynamic/run.sh

Closes: #2134
Approved by: bothra90

libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra