config.yaml.example is missing some AI plugins and has incorrect ordering

Description

Follow-up from #12926. While that PR fixed incorrect priority comments for ai-proxy, ai-proxy-multi, and ai-aws-content-moderation, there are still remaining issues in conf/config.yaml.example:

1. Missing AI plugins

The following plugins are registered in apisix/cli/config.lua but are not listed in config.yaml.example:

Plugin	Priority	Source
ai-request-rewrite	1073	apisix/plugins/ai-request-rewrite.lua
ai-aliyun-content-moderation	1029	apisix/plugins/ai-aliyun-content-moderation.lua

2. AI plugins not fully sorted by descending priority

The current AI plugin section in config.yaml.example:

  - ai-prompt-template             # priority: 1071
  - ai-prompt-decorator            # priority: 1070
  - ai-prompt-guard                # priority: 1072
  - ai-rag                         # priority: 1060
  - ai-aws-content-moderation      # priority: 1050
  - ai-proxy-multi                 # priority: 1041
  - ai-proxy                       # priority: 1040
  - ai-rate-limiting               # priority: 1030

ai-prompt-guard (priority 1072) should be listed before ai-prompt-template (priority 1071) to maintain descending priority order.

Expected result

After adding the missing plugins and fixing the order, the AI plugins section should look like:

  - ai-request-rewrite             # priority: 1073
  - ai-prompt-guard                # priority: 1072
  - ai-prompt-template             # priority: 1071
  - ai-prompt-decorator            # priority: 1070
  - ai-rag                         # priority: 1060
  - ai-aws-content-moderation      # priority: 1050
  - ai-proxy-multi                 # priority: 1041
  - ai-proxy                       # priority: 1040
  - ai-rate-limiting               # priority: 1030
  - ai-aliyun-content-moderation   # priority: 1029