[REFACTOR] Phase out legacy rust ffi

This PR phases out te legacy rust FFI as so we can focus on the new FFI,
and phase out legacy C APIs.
The change will allow us to move away from the legacy FFI API.
A new bindings can be built on top of new FFI later if there is
momentum on the direction.

Author: tqchen

ci/jenkins/generated/cpu_jenkinsfile.groovy

@@ -32,10 +32,6 @@
   cmake_build(ci_cpu, 'build')
   make_cpp_tests(ci_cpu, 'build')
   {{ m.upload_artifacts(tag='cpu', filenames=tvm_lib + tvm_allvisible + cpptest) }}
-  ci_setup(ci_cpu)
-  // sh "${docker_run} ${ci_cpu} ./tests/scripts/task_golang.sh"
-  // TODO(@jroesch): need to resolve CI issue will turn back on in follow up patch
-  sh (script: "${docker_run} ${ci_cpu} ./tests/scripts/task_rust.sh", label: 'Rust build and test')
 {% endcall %}
 
 {% set test_method_names = [] %}

ci/jenkins/templates/cpu_jenkinsfile.groovy.j2

@@ -131,8 +131,3 @@ tasks.
   ./docker/ci_build.sh ci_gpu make -C docs html
   ```
 
-- build golang test suite.
-
-  ```bash
-  ./docker/build.sh ci_cpu tests/scripts/task_golang.sh
-  ```