create network interfaces with a dedicated tag

[gaorong]

create network interfaces with a dedicated tag, which can greatly facilitate our life and well itegrate with other systems.
such as:

• Authorization system (e.g. RAM) can set up some policy based on tags. We trust our code, but we can not guarantee terway 100% bug-free, so we should set up a last defense by authorization policy to avoid terway to delete other people's ENI in some extreme case.
• We can also manipulate ENIs created by terway via tags: aliyun ecs DescribeNetworkInterfaces --RegionId cn-hangzhou --Tag.1.Key creater --Tag.1.Value terway. this may be helpful when there are lots of ENIs but most of them have no relationship with terway.

[codecov-io]

Codecov Report

Merging #64 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master     #64      +/-   ##
=========================================
- Coverage    6.13%   6.13%   -0.01%     
=========================================
  Files          31      31              
  Lines        3682    3685       +3     
=========================================
  Hits          226     226              
- Misses       3442    3445       +3     
  Partials       14      14

Impacted Files	Coverage Δ
pkg/aliyun/ecs.go	0% <0%> (ø)	⬆️

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