enhance: prevent CI root disk exhaustion

[sunby]

The build-space action left the runner root filesystem with only 100 MB free while allocating 100 GB to the workspace. Docker then failed to unpack the builder image with no space left on device, before any source compilation ran.

Replace the LVM allocation step in the build/test and code-check workflows with removal of unused preinstalled toolchains. Freed space remains available to Docker and the workspace. Restrict cleanup to GitHub-hosted runners using runner.environment.

Follow-up to #16. Failure log: https://github.com/sunby/milvus/actions/runs/34182547362/job/101924377699

Validation:

• Changed workflow steps pass actionlint v1.7.12 after filtering existing checkout-v2, intentionally disabled-job, and cache-action metadata diagnostics. The unfiltered baseline diagnostics remain.
• git diff --check and run_clang_format.sh passed. Unrelated formatter changes were discarded.
• make lint-fix ran and stopped at the existing local native-header mismatch in C.Analyze (four arguments versus three). No Go or C++ source is changed by this PR.
• A fresh CI run is needed to verify image extraction and subsequent build/test stages.