Remove index_in_caller and index_in_callee from InstructionAccount

[LucasSte]

Problem

Summary of Changes

Depends on #6829

[mergify]

The Firedancer team maintains a line-for-line reimplementation of the
native programs, and until native programs are moved to BPF, those
implementations must exactly match their Agave counterparts.
If this PR represents a change to a native program implementation (not
tests), please include a reviewer from the Firedancer team. And please
keep refactors to a minimum.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 96.81818% with 7 lines in your changes missing coverage. Please review.

Project coverage is 83.2%. Comparing base (4807a7a) to head (617622d).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6902   +/-   ##
=======================================
  Coverage    83.2%    83.2%           
=======================================
  Files         856      856           
  Lines      376390   376466   +76     
=======================================
+ Hits       313281   313347   +66     
- Misses      63109    63119   +10     

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