MAYA-127095 remove usage of macros leading to fatal exits

[pierrebai-adsk]

We should strive to reduce the number of scenarios under which Maya crashes. Instead, when possible, we should report an error to user and abort the operation. MayaUSD has extensive undo/redo capabilities now and code is able to undo partially done operations. Given this, errors should be reported and propagated back.

The macros TF_AXIOM and TF_FATAL_ERROR cause crashes when their conditions are not met, even in release builds. Remove TF_AXIOM and TF_FATAL_ERROR, replacing them with:

• TF_WARN when the situation was not an error but an unusual situation.
• TF_VERIFY when it still warrant an error message to the user, for example during error handling.
• Simple if/else, with an error return value when not a hard error.
• Simple if when the condition was trivial, like an empty node when iterating over USD nodes.
• In a few cases, TF_DEV_AXIOM when the condition was really strictly enforced by a class constructor.
• Entirely removed, when the code was already dealing with the error.
• C++ exception when the error needs to propagate to caller, in particular in constructors.