rename App.Handler to App.That

[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 adjusts the App.Handler to App.That and removes the App.HasHandler property. Because this property is no longer necessary

[codecov-io]

Codecov Report

Merging #242 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #242   +/-   ##
=======================================
  Coverage   97.63%   97.63%           
=======================================
  Files          37       37           
  Lines        2495     2495           
=======================================
  Hits         2436     2436           
  Misses         59       59

Impacted Files	Coverage Δ
src/CatLib.Core/CatLib/Application.cs	99.31% <100%> (ø)	⬆️
src/CatLib.Core/Container/BindData.cs	100% <0%> (ø)	⬆️
src/CatLib.Core/Container/Container.cs	99.67% <0%> (ø)	⬆️
src/CatLib.Core/Container/GivenData.cs	100% <0%> (ø)	⬆️
src/CatLib.Core/Container/MethodContainer.cs	100% <0%> (ø)	⬆️
src/CatLib.Core/Container/ExtendBindData.cs	100% <0%> (ø)	⬆️
src/CatLib.Core/CatLib/Facade.cs	94.87% <0%> (ø)	⬆️
src/CatLib.Core/Container/ExtendContainer.cs	100% <0%> (ø)	⬆️
src/CatLib.Core/EventDispatcher/EventDispatcher.cs	96.49% <0%> (ø)	⬆️
src/CatLib.Core/Container/Bindable.cs	98.14% <0%> (ø)	⬆️
... and 1 more

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