Refactor: Unifies ThisInvokeContext and dyn trait InvokeContext.

[Lichtso]

Problem

ThisInvokeContext is the only impl of trait InvokeContext

Summary of Changes

• Removes trait InvokeContext
• Renames ThisInvokeContext to InvokeContext
• Marks all ThisInvokeContext methods as pub and copies their doc comments from trait InvokeContext
• Adjusts the lifetimes of InvokeContext references.

Fixes #

[codecov]

Codecov Report

Merging #21563 (c69cad3) into master (c825b0a) will decrease coverage by 0.0%.
The diff coverage is 85.4%.

@@            Coverage Diff            @@
##           master   #21563     +/-   ##
=========================================
- Coverage    81.6%    81.6%   -0.1%     
=========================================
  Files         506      506             
  Lines      142368   142266    -102     
=========================================
- Hits       116232   116134     -98     
+ Misses      26136    26132      -4