terminal: Set `TERM_PROGRAM` and `TERM_PROGRAM_VERSION` environment variables in integrated terminal (#14213)

![image](https://github.com/zed-industries/zed/assets/31354274/9d1c5410-897b-40a1-8256-2d7e207f69ff)

These two environment variables are essential when people need to detect
terminal type and do something. Many popular terminals set them.

fixes https://github.com/zed-industries/zed/issues/4571

Release Notes:

- Set `TERM_PROGRAM` and `TERM_PROGRAM_VERSION` environment variables in
the integrated terminal
([#4571](https://github.com/zed-industries/zed/issues/4571)).