CDRIVER-4795 restore MONGOC_MD_FLAG_ENABLE_ICU

[kevinAlbs]

Summary

Restore the enum value MONGOC_MD_FLAG_ENABLE_ICU.

I suggest reviewing individual commits.

Additional improvements

parse_handshake_cfg.py is updated to support Python 3.

Explicit assignments are added to enum values (e.g. MONGOC_MD_FLAG_TRACE = 30 instead of MONGOC_MD_FLAG_TRACE) to clarify the values are fixed.

Background & Motivation

CDRIVER-4680 removed the MONGOC_MD_FLAG_ENABLE_ICU from the handshake config.

The handshake config is reported in the client metadata sent to the server. Here are examples from the mongod logs (search for "cfg"):

{"t":{"$date":"2023-12-13T13:00:39.283-05:00"},"s":"I",  "c":"NETWORK",  "id":51800,   "ctx":"conn13","msg":"client metadata","attr":{"remote":"127.0.0.1:49998","client":"conn13","doc":{"driver":{"name":"mongoc","version":"1.24.3"},"os":{"type":"Darwin","name":"macOS","version":"21.6.0","architecture":"arm64"},"platform":"cfg=0x0300deaa65 posix=200112 stdc=199901 CC=clang 14.0.0 (clang-1400.0.29.202) CFLAGS=\"\" LDFLAGS=\"\""}}}
{"t":{"$date":"2023-12-13T13:00:39.374-05:00"},"s":"I",  "c":"NETWORK",  "id":51800,   "ctx":"conn14","msg":"client metadata","attr":{"remote":"127.0.0.1:50000","client":"conn14","doc":{"driver":{"name":"mongoc","version":"1.25.0"},"os":{"type":"Darwin","name":"macOS","version":"21.6.0","architecture":"arm64"},"platform":"cfg=0x0383d6aa65 posix=200112 stdc=199901 CC=clang 14.0.0 (clang-1400.0.29.202) CFLAGS=\"\" LDFLAGS=\"\""}}}

MONGOC_MD_FLAG_ENABLE_ICU was likely unintentionally removed. Removing shifted the subsequent values down one. This may add difficultly parsing and comparing config values between driver versions.