wip: replace use of attest-mock binary w/ API

.github/buildomat/jobs/build-and-test.sh

@@ -12,10 +12,4 @@ set -o xtrace
 cargo --version
 rustc --version
 
-# dependency used by `build.rs` to build measurement log & corpus
-cargo install --locked \
-    --git https://github.com/oxidecomputer/dice-util \
-    --rev 4b408edc1d00f108ddf635415d783e6f12fe9641 \
-    attest-mock
-
 cargo test

.github/workflows/rust.yml

@@ -43,12 +43,6 @@ jobs:
         run: cargo --version
       - name: Report rustc version
         run: rustc --version
-      - name: Install attest-mock
-        run: |
-          cargo install --locked \
-            --git https://github.com/oxidecomputer/dice-util \
-            --rev 4b408edc1d00f108ddf635415d783e6f12fe9641 \
-            attest-mock
       - name: Build
         run: cargo build --all-targets --verbose
       - name: Run tests