[ci] Migrate to sonicbld1es agent pool. (sonic-net#397) (sonic-net#402)

Old agent pool is deprecated. Migrate to new agent pool.

Co-authored-by: Liu Shilong <shilongliu@microsoft.com>

.azure-pipelines/build-template.yml

@@ -16,11 +16,11 @@ parameters:
 - name: pool
   type: string
   values:
-  - sonicbld
+  - sonicbld-1es
   - sonicbld_8c
   - sonicbld-arm64
   - sonicbld-armhf
-  default: sonicbld
+  default: sonicbld-1es
 
 - name: timeout
   type: number