chore: use ubuntu-slim for lightweight jobs (#3107)

ubuntu-slim is a new cost-efficient runner to fit lightweight jobs. We
can use this to save ASF infra usage (if possible).

By *lightweight* I mean jobs that run for less than a minute and are not
easily affected by other concurrently running jobs on the same host.

This topic was raised in the Apache ORC project and later adopted by
iceberg-cpp. We believe it could also benefit other projects under the
Apache Iceberg umbrella.

Refs:

-
https://github.blog/changelog/2025-10-28-1-vcpu-linux-runner-now-available-in-github-actions-in-public-preview/
-
https://github.com/actions/runner-images/blob/main/images/ubuntu-slim/ubuntu-slim-Readme.md

Author: zhjwpku

.github/workflows/codeql.yml

@@ -33,7 +33,7 @@ permissions:
 jobs:
   analyze:
     name: Analyze Actions
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
     permissions:
       contents: read
       security-events: write

.github/workflows/python-ci-docs.yml

@@ -35,7 +35,7 @@ concurrency:
 
 jobs:
   docs:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-slim
 
     steps:
       - uses: actions/checkout@v6