build: Enable pxr_boost::python for Python bindings #6

Job	Run time
Linux (cp37, /opt/python/cp37-cp37m/bin/python, 3.7)	26m 53s
macOS (3.7, python3.7, cp37)	46m 27s
macOS (3.8, python3.8, cp38)	49m 47s
macOS (3.9, python3.9, cp39)	39m 21s
Linux (cp38, /opt/python/cp38-cp38/bin/python, 3.8)	25m 35s
macOS (3.10, python3.10, cp310)	49m 56s
Linux (cp39, /opt/python/cp39-cp39/bin/python, 3.9)	25m 57s
macOS (3.11, python3.11, cp311)	43m 22s
Linux (cp310, /opt/python/cp310-cp310/bin/python, 3.10)	25m 53s
Linux (cp311, /opt/python/cp311-cp311/bin/python, 3.11)	26m 15s
Windows (3.7, cp37)	28m 10s
Windows (3.8, cp38)	28m 26s
Windows (3.9, cp39)	28m 20s
Windows (3.10, cp310)	28m 2s
Windows (3.11, cp311)	28m 3s
CollectPackages	17s
Test (Linux_Python37, 3.7, ubuntu-20.04, python3)	20s
Test (Linux_Python38, 3.8, ubuntu-20.04, python3)	28s
Test (Linux_Python39, 3.9, ubuntu-20.04, python3)	33s
Test (Linux_Python310, 3.10, ubuntu-20.04, python3)	23s
Test (Linux_Python311, 3.11, ubuntu-20.04, python3)	35s
Test (Mac_Python37, 3.7, macos-12, python3)	36s
Test (Mac_Python38, 3.8, macos-12, python3)	37s
Test (Mac_Python39, 3.9, macos-12, python3)	37s
Test (Mac_Python310, 3.10, macos-12, python3)	32s
Test (Mac_Python311, 3.11, macos-12, python3)	41s
Test (Windows_Python37, 3.7, windows-2019, python3)	37s
Test (Windows_Python38, 3.8, windows-2019, python3)	36s
Test (Windows_Python39, 3.9, windows-2019, python3)	36s
Test (Windows_Python310, 3.10, windows-2019, python3)	31s
Test (Windows_Python311, 3.11, windows-2019, python3)	35s
	8h 29m 1s

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