Drop the SHT_NOTE section search from findExecFn

[godlygeek]

findExecFn searched a core file's SHT_NOTE sections for the auxiliary vector before falling back to its PT_NOTE segments, on the grounds that "in a core file, the program headers may not be reliable". The section search could never find anything the segment search doesn't, so drop it.

It always failed because it gave an Elf_Data with a d_type of ELF_T_NHDR or ELF_T_NHDR8 to parseCoreExecfn, which passed that Elf_Data to gelf_getauxv, which rejects any Elf_Data whose d_type isn't ELF_T_AUXV. If it weren't rejected explicitly it still wouldn't work; we're passing a sequence of notes with leading headers to a function that expects to be pointed directly at a single note's payload.

Repairing it would have gained us nothing. For a core file the program headers are the authoritative structure, not the section headers:

• Cores written by the kernel never have SHT_NOTE sections.
• gcore cores have an SHT_NOTE section that matches the PT_NOTE segment.
• If a core somehow did have an SHT_NOTE section but no PT_NOTE segments then findExecFn would never be reached: dwfl_core_file_attach requires a PT_NOTE program header, and the CoreFileAnalyzer constructor throws when dwfl_core_file_attach fails.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.78%. Comparing base (ba81703) to head (3ee0302).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #368   +/-   ##
=======================================
  Coverage   78.77%   78.78%           
=======================================
  Files          58       58           
  Lines        6715     6694   -21     
  Branches      635      630    -5     
=======================================
- Hits         5290     5274   -16     
+ Misses       1425     1420    -5     

Flag	Coverage Δ
cpp	78.78% <100.00%> (+<0.01%)	⬆️
python	78.78% <100.00%> (+<0.01%)	⬆️

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[pablogsal]

Damn good find!