[API] chocolatey.lib clobbers TMP and TEMP environment variables,

### What You Are Seeing?

I use `List()` to retrieve the installation status of some packages within my application and it modifies the `TMP` environment variable for the whole application because `set_environment_variables()` is called.

As a result, any process launched by my application get the wrong temporary directory.

### What is Expected?
`TMP` or `TEMP` should not be modified by a library; if subprocesses need them, maybe use `ProcessStartInfo.EnvironmentVariables`?

### How Did You Get This To Happen? (Steps to Reproduce)
```c#
m_choco = Lets.GetChocolatey();
```
```c#
m_choco.Set(conf =>
{
conf.CommandName = "info";
conf.ListCommand.LocalOnly = local;
conf.Input = package_name;
conf.RegularOutput = false; // disable messages about pro/business version (QuietOutput does not work)
}).List()
/* ... */
```

Start at the implementation reached by Lets.GetChocolatey().Set(...).List(), then locate where set_environment_variables() is called. Review whether ProcessStartInfo.EnvironmentVariables can scope subprocess values, and verify that calling List() leaves the application's TMP and TEMP unchanged.

Written by the indexing model from the issue text.