add Guard expandable supported.

[ymh199478]

Q	A
Branch?	v2.0(master)
Bug fix?	No
New feature?	No
Deprecations?	No
Internal Changed?	Yes
Removed	No
Tests pass?	Yes
Doc pr?	No

This commit allows the Guard class to be extended by developers to extend the Guard by extension functions.

[codecov-io]

Codecov Report

Merging #233 into master will decrease coverage by 0.1%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master    #233      +/-   ##
=========================================
- Coverage   96.01%   95.9%   -0.11%     
=========================================
  Files          31      31              
  Lines        2659    2662       +3     
=========================================
  Hits         2553    2553              
- Misses        106     109       +3

Impacted Files	Coverage Δ
src/CatLib.Core/Support/Guard/Guard.cs	84.21% <0%> (-15.79%)	⬇️

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