inline-spl: add amount

[2501babe]

prereq for my latest balance collection concept. we may also want to add mint parsing and get mint decimals here, but not strictly necessary

i think i want better dispatch for the two structs, the pattern is a bit strange. you should be able to pass in program_id and get the right one

Problem

Summary of Changes

Fixes #

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 83.3%. Comparing base (8cdbb4f) to head (d2c6b59).
Report is 60 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5587   +/-   ##
=======================================
  Coverage    83.3%    83.3%           
=======================================
  Files         821      821           
  Lines      372264   372273    +9     
=======================================
+ Hits       310355   310396   +41     
+ Misses      61909    61877   -32     

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[2501babe]

inline-spl changes are superceded by solana-program/libraries#70, once that lands and has a release we can remove inline-spl from agave