exposing max_raw_memory_mb

[ankmachine]

Description

Tests

Checklist:

• I have read the contribution guidelines.
• I have updated the documentation, if applicable. (Check if there is no
  need to update the documentation, for example if this is a bug fix that
  doesn't change the API.)
• I have ensured that the change is tested somewhere in the testsuite
  (adding new test cases if necessary).
• If I added or modified a C++ API call, I have also amended the
  corresponding Python bindings (and if altering ImageBufAlgo functions, also
  exposed the new functionality as oiiotool options).
• My code follows the prevailing code style of this project. If I haven't
  already run clang-format before submitting, I definitely will look at the CI
  test that runs clang-format and fix anything that it highlights as being
  nonconforming.

[linux-foundation-easycla]

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[ankmachine]

closing this as i have created a new PR with proper CLA approved workflow here #4454