Some boost headers are unused

[nvmkuruc]

Description of Issue

The following headers are included but unused in pxr.

boost/preprocessor/arithmetic/add.hpp
boost/preprocessor/tuple/eat.hpp
boost/preprocessor/seq/push_back.hpp
boost/assign.hpp
boost/mpl/or.hpp
boost/ptr_container/ptr_map.hpp

Removing them reduces the number of dependencies on boost.

Steps to Reproduce

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System Information (OS, Hardware)

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Package Versions

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Build Flags

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[nvmkuruc]

I have a fix.

[tallytalwar]

Filed as internal issue #USD-7971

[nvmkuruc]

I think we can close this. Any unused headers are now transitive through tf/preprocessorUtils.h and vt/functions.h