[frontend-gray] Increase gray types according to the ratio-weight gray

[heimanba]

Ⅰ. Describe what this PR did

1. 增加按照比例灰度的能力,YAML配置如下：
   灰度规则 beta-user的灰度范围为 50%

baseDeployment: 
  version: "dev"
grayDeployments: 
- name: "beta-user"
  version: "0.0.1"
  enabled: "true"
  weight: "50"

2. 添加往首页注入脚本的能力
   可以分别在 header，body的首部first和尾部last注入相关代码。

---
injection: 
  header: 
  - "<script>console.log('Header')</script>"
  body: 
    first: 
    - "<script>console.log('hello world before')</script>"
    - "<script>console.log('hello world before1')</script>"
    last: 
    - "<script>console.log('hello world after')</script>"
    - "<script>console.log('hello world after2')</script>"

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)?

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.31%. Comparing base (ef31e09) to head (1de8d96).
Report is 106 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1291      +/-   ##
==========================================
+ Coverage   35.91%   44.31%   +8.40%     
==========================================
  Files          69       75       +6     
  Lines       11576     9823    -1753     
==========================================
+ Hits         4157     4353     +196     
+ Misses       7104     5142    -1962     
- Partials      315      328      +13     

see 90 files with indirect coverage changes

[CH3CHO]

LGTM