feat: Add earthfile for vit-testing | NPG-0000 (#576)

# Description

Adding a earthfile to vit-testing. This is needed to enable the build of
backend artifacts in the catalyst-artifacts repo


## Type of change

Please delete options that are not relevant.

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?

Runned on my local machine

## Checklist

- [x ] My code follows the style guidelines of this project
- [x ] I have performed a self-review of my code
- [x ] I have commented my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

src/vit-testing/Earthfile

@@ -0,0 +1,12 @@
+VERSION 0.7
+
+build:
+    FROM ../../+builder
+    RUN cargo build --locked --release -p iapyx -p valgrind -p vitup
+
+    # Store the artifact
+    SAVE ARTIFACT /src/target/release/iapyx iapyx
+    SAVE ARTIFACT /src/target/release/iapyx-load iapyx-load
+    SAVE ARTIFACT /src/target/release/valgrind valgrind
+    SAVE ARTIFACT /src/target/release/vitup vitup
+    SAVE IMAGE --cache-hint