[In progress] Free nodes as they're parsed in program.from_value()

[kahmed10]

The aim of this PR is to try to free memory as nodes are parsed.

Not working as intended currently, as there's no difference in memory usage.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3749      +/-   ##
===========================================
+ Coverage    92.16%   92.81%   +0.65%     
===========================================
  Files          515      520       +5     
  Lines        21978    23738    +1760     
===========================================
+ Hits         20256    22032    +1776     
+ Misses        1722     1706      -16     

Files with missing lines	Coverage Δ
src/include/migraphx/program.hpp	100.00% <ø> (ø)
src/include/migraphx/value.hpp	92.00% <100.00%> (+0.08%)	:arrow_up:
src/program.cpp	70.29% <100.00%> (+0.09%)	:arrow_up:

... and 30 files with indirect coverage changes

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