Add environment variable before terminal creation for REPL

[anthonykim1]

We need to be able to add environment variables such as PYTHONSTARTUP, in order to run Python code needed for shell integration.

[anthonykim1]

Closing as completed since we can pass in environment variable via:

 this.terminal = this.terminalManager.createTerminal({
            name: this.options?.title || 'Python',
            env: { PYTHONSTARTUP: this.envVarScript },
            hideFromUser: this.options?.hideFromUser,
        });