Undo inlining of TfIsUtf8CodePointXid{Start,Continue}

[nvmkuruc]

Description of Change(s)

#2857 was focused on reducing the cost / instruction count of initializing the range tables for the Xid character classes. It also inlined their usage in unicodeUtils.{h,cpp}. However, unicodeCharacterClasses is private and cannot be included in the header for unicodeUtils to be used outside of Tf.

This rolls back just that part of #2857.

It also removes the dependency on the TF_MAX_CODE_POINT symbol inherited from unicodeCharacterClasses to avoid including the private header in the test case.

Fixes Issue(s)

• I have verified that all unit tests pass with the proposed changes

• I have submitted a signed Contributor License Agreement

[tallytalwar]

Filed as internal issue #USD-9114

[dsyu-pixar]

Please ignore -- my review comment (for PR 2888) was accidentally copied here as well.