[CI] Revert speedup image building and CI Installation related PRs (#6891)

### What this PR does / why we need it?

Revert speedup image building and CI Installation related PRs

git revert 8835236181
git revert 64fba51275
git revert 263c2f8e8d
git revert 84b00695f8


### Does this PR introduce _any_ user-facing change?

### How was this patch tested?

- vLLM version: v0.16.0
- vLLM main:
15d76f74e2

---------

Signed-off-by: wjunLu <wjunlu217@gmail.com>

.github/workflows/_schedule_image_build.yaml

@@ -76,28 +76,6 @@ jobs:
         driver: docker-container
         use: true
 
-    - name: Set cache ref
-      id: cache
-      run: |
-        if [ "${{ github.ref_type }}" = "tag" ]; then
-          # For tag events, use the images built from source branch as cache (the tag image doesn't exist yet).
-          if [ -z "$branch" ]; then
-            branch=$(git branch -r --contains HEAD \
-              | grep -v 'HEAD' \
-              | sed 's|[[:space:]]*origin/||' \
-              | head -1)
-          fi
-          branch="${branch:-main}"
-        else
-          # For PR events github.ref_name is "<PR_number>/merge" which has no cached image;
-          # use base_ref (target branch) instead. For push/schedule, base_ref is empty so
-          # fall back to ref_name which is the actual branch name.
-          branch="${{ github.base_ref || github.ref_name }}"
-        fi
-        # Replace / with - for use in image tags
-        branch="${branch//\//-}"
-        echo "ref=quay.io/ascend/vllm-ascend:${branch}-${{ inputs.suffix }}" >> $GITHUB_OUTPUT
-
     - name: Build and push
       uses: docker/build-push-action@v6
       id: build
@@ -111,8 +89,6 @@ jobs:
         outputs: type=image,name=quay.io/ascend/vllm-ascend,push-by-digest=true,name-canonical=true,push=${{ inputs.should_push }}
         build-args: |
           PIP_INDEX_URL=https://pypi.org/simple
-        # use previously pushed multi-arch image as cache to speed up builds
-        cache-from: type=registry,ref=${{ steps.cache.outputs.ref }}
         provenance: false
 
     - name: Export digest
@@ -178,7 +154,6 @@ jobs:
           #      which follow the rule from vLLM with prefix v
           # TODO(yikun): the post release might be considered as latest release
           tags: |
-            type=ref,event=branch,suffix=${{ env.SUFFIX }}
             type=pep440,pattern={{raw}},suffix=${{ env.SUFFIX }}
             type=schedule,pattern=main,suffix=${{ env.SUFFIX }}
             type=raw,value=${{ inputs.workflow_dispatch_tag }},enable=${{ github.event_name == 'workflow_dispatch' }},suffix=${{ env.SUFFIX }}