[CT-1806] [Spike] Measure usage of certain functions(os.environ, os.path)

[ChenyuLInx]

After API-ification is merged to main, search in the codebase and figure out where are the following functions still being called in dbt-core after we create the Flags object. Ideally, we would like to get all of those information before Flags are being constructed and store it either inside Flags or some other object.

• os.path
• os.envvar
• functions to read or write files(optional)

[jtcohen6]

Closely related, with some more context: #6544 + #6545

We may want different mechanisms for "reading" files (accepting data as inputs), versus "writing" files (publishing data to a log/stream/...)