Fix: Codebuild UnitTest

[williamputraintan]

general:

• Commenting out staging and prod environment in stateless stack - stateful resource does not exist (in stg and prod) and the stateless lookup will fail the pipeline

metadata_manager:

• mark external dependencies for lambda runtime dependencies (to prevent unresolved path when bundling)

filemanager:

• Rust installation for codebuild unit test && cargo-lambda
• disable cdk-nag for filemanager due to rust.aws-cdk-lambda do not have .toString() function which causes an error - it was due to compilation error led to the lambda construct to be undefined but is fixed on subsequent commit/pr

[mmalenic]

Related to #124. I think the Rust compilation is failing because of the --all-targets --all-features which compiles the tests in the Makefile.