Make the test suite pass on Windows

The Filesystem module stored the paths of an iOS dump with the separator
of the system checking it, so on Windows the process and file path
indicators, which split paths on "/", never matched. It now stores them
as POSIX paths.

The rest are test fixes:
- the completion install tests also redirect USERPROFILE, which
  Path.home() reads on Windows; they wrote to the real home folder;
- the plugin table helpers accept the light header Rich draws on
  consoles that cannot show the heavy one;
- the completion test quotes the command path, whose backslashes were
  dropped when COMP_WORDS was split;
- tests that need symbolic links or the sqlite3 binary are skipped when
  those are not available;
- two assertions no longer depend on the path separator or on the line
  ending text mode writes.

tests/common/test_cli_plugins.py

@@ -1,3 +1,4 @@
+import shlex
 from types import SimpleNamespace
 
 import click
@@ -110,7 +111,7 @@ def test_load_command_option_supports_folders_and_repeated_paths(tmp_path):
 def test_loaded_command_participates_in_shell_completion(tmp_path):
     command_path = _write_command(tmp_path / "hello.py", "hello")
     group = _make_group()
-    words = f"group --load-command {command_path} he"
+    words = f"group --load-command {shlex.quote(str(command_path))} he"
 
     result = CliRunner().invoke(
         group,

tests/common/test_cmd_plugins.py

@@ -1,4 +1,5 @@
 import json
+import re
 from types import SimpleNamespace
 
 import pytest
@@ -54,20 +55,23 @@ def _run(command, arguments):
     return CliRunner().invoke(command, arguments, env={"COLUMNS": "200"})
 
 
-def _table_rows(output):
-    """Return the content of the table rows, without the header and the box."""
+def _table_lines(output):
+    """Return the cells of each line of the table, header first."""
     return [
-        [cell.strip() for cell in line.strip().strip("│").split("│")]
+        [cell.strip() for cell in re.split("[│┃]", line.strip().strip("│┃"))]
         for line in output.splitlines()
-        if "│" in line
+        if "│" in line or "┃" in line
     ]
 
 
+def _table_rows(output):
+    """Return the content of the table rows, without the header and the box."""
+    return _table_lines(output)[1:]
+
+
 def _table_header(output):
-    for line in output.splitlines():
-        if "┃" in line:
-            return [cell.strip() for cell in line.strip().strip("┃").split("┃")]
-    return []
+    lines = _table_lines(output)
+    return lines[0] if lines else []
 
 
 def _install(monkeypatch, distributions, entry_points):