Disable debug information on CI (#6356)

In #6338 that PR is bouncing on CI due to Windows running out of disk
space. Locally a `./ci/run-tests.sh` compile produces a ~13G build
directory. Testing on CI it looks like Windows builders have ~13G of
free space on them for GitHub Actions. I think something in that PR has
tipped us just over the edge of requiring too much space, although I'm
not sure exactly what.

To address the issue this commit disables DWARF debug information
entirely on all builders on CI. Not only should this save a sliver of
compile time but this reduces a local build directory to ~4.7G, over a
50% reduction. That should keep us fitting in CI for more time to come
hopefully.

.github/actions/install-rust/action.yml

@@ -23,11 +23,11 @@ runs:
         rustup default "${{ inputs.toolchain }}"
 
         # Save disk space by avoiding incremental compilation. Also turn down
-        # debuginfo from 2 to 1 to help save disk space.
+        # debuginfo from 2 to 0 to help save disk space.
         cat >> "$GITHUB_ENV" <<EOF
         CARGO_INCREMENTAL=0
-        CARGO_PROFILE_DEV_DEBUG=1
+        CARGO_PROFILE_DEV_DEBUG=0
-        CARGO_PROFILE_TEST_DEBUG=1
+        CARGO_PROFILE_TEST_DEBUG=0
         EOF
 
         # Deny warnings on CI to keep our code warning-free as it lands in-tree.