Support use /dev/stdin as SOURCE path for image build

[zyfjeff]

Relevant Issue (if applicable)

If there are Issues related to this PullRequest, please list it.

Details

Support use /proc/self/fd/0 as SOURCE path for image build

Types of changes

What types of changes does your PullRequest introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist

Go over all the following points, and put an x in all the boxes that apply.

• I have updated the documentation accordingly.
• I have added tests to cover my changes.

[codecov]

Codecov Report

Merging #1407 (92239eb) into master (1abf0ae) will increase coverage by 0.00%.
The diff coverage is 71.42%.

@@           Coverage Diff           @@
##           master    #1407   +/-   ##
=======================================
  Coverage   46.45%   46.46%           
=======================================
  Files         123      123           
  Lines       38602    38607    +5     
  Branches    38602    38607    +5     
=======================================
+ Hits        17931    17937    +6     
+ Misses      19702    19696    -6     
- Partials      969      974    +5     

Files Changed	Coverage Δ
src/bin/nydus-image/main.rs	41.58% <71.42%> (+0.59%)	⬆️

... and 4 files with indirect coverage changes