chore: Use rust-license-tool for license file (#741)

# Motivation
The license check often fails, which requires extra engineering time to
fix.

# This PR
Switch to using Datadog's `rust-license-tool` to manage the license
file. https://github.com/DataDog/rust-license-tool
This replaces `bottlecap/LICENSE-3rdparty.yml` with
`bottlecap/LICENSE-3rdparty.csv`.

# Testing
## Success case
Run this workflow on `yiming.luo/csv-license` branch, which was
successful

https://github.com/DataDog/datadog-lambda-extension/actions/runs/16274305134

## Failure case
Delete a line in the license file then run the workflow, which failed as
expected

https://github.com/DataDog/datadog-lambda-extension/actions/runs/16274444263

Author: lym953

.github/workflows/rs_ci.yml

@@ -157,62 +157,13 @@ jobs:
       - working-directory: bottlecap
         run: cargo fmt --all -- --check
 
-  # todo: fix upstream warnings; from the readme:
-  # The most common cause of missing licenses seems to be workspaces that
-  # don't include forward their license files. Go to the repo for the
-  # workspace and copy the relevant files from there.
-  # A package license may receive a confidence warning stating that
-  # cargo-bundle-licenses is "unsure" or "semi" confident. This means that
-  # when the found license was compared to a template license it was found to
-  # have diverged in more than a few words. You should verify that the licence
-  #  text is in fact correct in these cases.
-  #
-  # If this job fails, you probably need to regenerate the license, e.g.
-  # CARGO_HOME=/tmp/dd-cargo cargo bundle-licenses --format yaml --output LICENSE-3rdparty.yml
+  # If this fails, run `dd-rust-license-tool write` in bottlecap/
   license-3rdparty:
     runs-on: ubuntu-22.04
-    name: "Valid LICENSE-3rdparty.yml"
+    name: "Valid LICENSE-3rdparty.csv"
     steps:
       - name: Checkout sources
         uses: actions/checkout@v4
-      - run: stat LICENSE-3rdparty.yml
+      - run: cargo install dd-rust-license-tool --locked
+      - run: dd-rust-license-tool check
         working-directory: bottlecap
-      - name: Cache
-        uses: actions/cache@v4
-        with:
-          path: |
-            ~/.cargo/registry/
-            ~/.cargo/git/db/
-            ~/.cargo/bin/
-            ~/.cargo/.crates.toml
-          # cache key contains current version of cargo-bundle-licenses
-          # when upstream version is updated we can bump the cache key version,
-          # to cache the latest version of the tool
-          key: "v1-2.2.0"
-      # cargo-bundle-licenses v2.0 doesn't understand path differences due to
-      # sparse vs git index, so force git.
-      - run: sudo apt-get update && sudo apt-get upgrade
-      - run: mkdir -p .cargo && printf "[registries.crates-io]\nprotocol = \"git\"\n" > .cargo/config.toml
-        working-directory: bottlecap
-      - run: cargo install cargo-bundle-licenses
-      - name: "Generate new LICENSE-3rdparty.yml and check against the previous"
-        working-directory: bottlecap
-        env:
-          CARGO_HOME: "/tmp/dd-cargo"
-        run: |
-          # Run cargo bundle-licenses without directly checking against a previous snapshot
-          cargo bundle-licenses \
-            --format yaml \
-            --output /tmp/CI.yaml
-
-          # Normalize the paths in both files to ignore registry differences
-          sed -E 's/(registry\/src\/)[^\/]+/\1normalized_path/g' /tmp/CI.yaml > /tmp/CI_normalized.yaml
-          sed -E 's/(registry\/src\/)[^\/]+/\1normalized_path/g' LICENSE-3rdparty.yml > /tmp/LICENSE-3rdparty_normalized.yml
-
-          # Now perform the diff on the normalized files
-          if ! diff /tmp/CI_normalized.yaml /tmp/LICENSE-3rdparty_normalized.yml; then
-            echo "Differences detected."
-            exit 1
-          fi
-
-          echo "No differences found."