add source element type in accesspath

[jumormt]

This patch adds a field sourceElementType in accesspath, e.g.,

%f1 = getelementptr inbounds %struct.MyStruct, %struct.MyStruct* %arrayidx, i32 0, i32 0

The source element type is %struct.MyStruct

This is also useful for the migration regarding opaque pointers (https://llvm.org/docs/OpaquePointers.html#migration-instructions).

[codecov]

Codecov Report

Merging #1269 (e6ecc02) into master (7a3e537) will increase coverage by 0.00%.
Report is 4 commits behind head on master.
The diff coverage is 65.51%.

❗ Current head e6ecc02 differs from pull request most recent head 9f45edc. Consider uploading reports for the commit 9f45edc to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1269   +/-   ##
=======================================
  Coverage   64.49%   64.49%           
=======================================
  Files         223      223           
  Lines       23789    23798    +9     
=======================================
+ Hits        15342    15349    +7     
- Misses       8447     8449    +2     

Files	Coverage Δ
svf-llvm/lib/SVFIRBuilder.cpp	78.28% <100.00%> (+0.13%)	⬆️
svf/include/Graphs/ConsGEdge.h	84.21% <100.00%> (ø)
svf/lib/DDA/ContextDDA.cpp	68.46% <100.00%> (ø)
svf/lib/DDA/FlowDDA.cpp	69.56% <100.00%> (ø)
svf/lib/SVFIR/SVFIR.cpp	79.35% <ø> (ø)
svf/lib/WPA/Andersen.cpp	89.83% <100.00%> (ø)
svf/lib/WPA/FlowSensitive.cpp	78.01% <100.00%> (ø)
svf-llvm/lib/SVFIRExtAPI.cpp	80.14% <83.33%> (+0.14%)	⬆️
svf/include/MemoryModel/AccessPath.h	78.57% <80.00%> (-4.77%)	⬇️
svf/include/SVFIR/SVFStatements.h	83.00% <0.00%> (ø)
... and 2 more