env: rename "system" to "base" in output of env info

docs/managing-environments.md

@@ -88,13 +88,13 @@ poetry env info
 will output something similar to this:
 
 ```text
-Virtual environment
+Virtualenv
 Python:         3.7.1
 Implementation: CPython
 Path:           /path/to/poetry/cache/virtualenvs/test-O3eWbxRl-py3.7
 Valid:          True
 
-System
+Base
 Platform: darwin
 OS:       posix
 Python:   /path/to/main/python

src/poetry/console/commands/env/info.py

@@ -71,15 +71,15 @@ def _display_complete_info(self, env: Env) -> None:
 
         self.line("")
 
-        system_env = env.parent_env
-        python = ".".join(str(v) for v in system_env.version_info[:3])
-        self.line("<b>System</b>")
+        base_env = env.parent_env
+        python = ".".join(str(v) for v in base_env.version_info[:3])
+        self.line("<b>Base</b>")
         self.line(
             "\n".join([
                 f"<info>Platform</info>:   <comment>{env.platform}</>",
                 f"<info>OS</info>:         <comment>{env.os}</>",
                 f"<info>Python</info>:     <comment>{python}</>",
-                f"<info>Path</info>:       <comment>{system_env.path}</>",
-                f"<info>Executable</info>: <comment>{system_env.python}</>",
+                f"<info>Path</info>:       <comment>{base_env.path}</>",
+                f"<info>Executable</info>: <comment>{base_env.python}</>",
             ])
         )

tests/console/commands/env/test_info.py

@@ -43,7 +43,7 @@ def test_env_info_displays_complete_info(tester: CommandTester) -> None:
 Executable:     {sys.executable}
 Valid:          True
 
-System
+Base
 Platform:   darwin
 OS:         posix
 Python:     {'.'.join(str(v) for v in sys.version_info[:3])}