Use `EnvObj` methods instead of `Theory` methods (#7144)

Use `EnvObj` methods instead of `Theory` methods (#7144)

This removes the methods `getEnv()`, `options()`, `getSatContext()`, and
`getUserContext()` from the `Theory` class because they are now part of
`EnvObj`. Additionally, this commit converts the inference managers to
`EnvObj` because of there were some calls to retrieve the contexts from
`Theory` in those classes.