PYTHON-2110 Refactored some C to avoid symbol conflicts

[bcwarner]

Refactored some of the C symbols so that they avoid conflicts as mentioned in PYTHON-2110. The following symbols should be refactored as:

PyInit__cmessage        => pymongo_PyInit__cmessage
buffer_free             => pymongo_buffer_free
buffer_get_buffer       => pymongo_buffer_get_buffer
buffer_get_position     => pymongo_buffer_get_position
buffer_new              => pymongo_buffer_new
buffer_save_space       => pymongo_buffer_save_space
buffer_update_position  => pymongo_buffer_update_position
buffer_write            => pymongo_buffer_write

PyInit__cmessage        => pymongo_PyInit__cmessage
buffer_free             => pymongo_buffer_free
buffer_get_buffer       => pymongo_buffer_get_buffer
buffer_get_position     => pymongo_buffer_get_position
buffer_new              => pymongo_buffer_new
buffer_save_space       => pymongo_buffer_save_space
buffer_update_position  => pymongo_buffer_update_position
buffer_write            => pymongo_buffer_write
check_string            => cbson_check_string
cmp_date                => cbson_cmp_date
convert_type_registry   => cbson_convert_type_registry
copy_TM64_to_tm         => cbson_copy_TM64_to_tm
copy_tm_to_TM64         => cbson_copy_tm_to_TM64
date_in_safe_range      => cbson_date_in_safe_range
fake_localtime_r        => cbson_fake_localtime_r
gmtime64                => cbson_gmtime64
gmtime64_r              => cbson_gmtime64_r
localtime64             => cbson_localtime64 
localtime64_r           => cbson_localtime64_r
mktime64                => cbson_mktime64
timegm64                => cbson_timegm64
timelocal64             => cbson_timelocal64
valid_tm_mon            => cbson_valid_tm_mon
valid_tm_wday           => cbson_valid_tm_wday

[ShaneHarvey]

Nice work so far! Looking at the test failures in Evergreen (our CI system), it appears the PyInit_ functions need to be changed back:

[2022/06/09 20:05:14.193] + /opt/python/3.10/bin/python3 setup.py build_ext -i
[2022/06/09 20:05:14.193] + /opt/python/3.10/bin/python3 -c 'from bson import _cbson; from pymongo import _cmessage'
[2022/06/09 20:05:14.296] Traceback (most recent call last):
[2022/06/09 20:05:14.296]   File "<string>", line 1, in <module>
[2022/06/09 20:05:14.296] ImportError: dynamic module does not define module export function (PyInit__cbson)
[2022/06/09 20:05:14.306] Command failed: shell script encountered problem: exit code 1

https://spruce.mongodb.com/task/mongo_python_driver_tests_python_version_ubuntu18_test_ssl__platform~ubuntu_18.04_auth_ssl~auth_ssl_python_version~3.10_coverage~coverage_test_3.6_standalone_patch_b8653b018d0f16f2f60640a633c832939fffccbe_62a251fe9ccd4e36ab48f80b_22_06_09_20_03_11/logs?execution=0&sortBy=STATUS&sortDir=ASC

[ShaneHarvey]

LGTM!

[juliusgeo]

LGTM!