Remove private module stubs and their re-exports

Judgement calls — removed:

- sampling/_css_utils.pyi: deleted — private module (_css_utils) used
  only internally by stack_collector and heatmap_collector; get_combined_css
  is not part of any public API
- sampling/_format_utils.pyi: deleted — private module (_format_utils)
  used only internally; fmt is a simple formatting helper not intended
  for external use
- sampling/_sync_coordinator.pyi: deleted — private module only containing
  main() -> Never, which is a subprocess entry point never called externally
- sampling/_child_monitor.pyi: removed get_child_pids and is_python_process
  — private utility functions used only inside _child_monitor itself;
  ChildProcessMonitor kept because it is re-exported from cli.pyi
- sampling/heatmap_collector.pyi: removed re-exports of get_combined_css
  and fmt — these are private implementation imports, not part of
  HeatmapCollector's public API
- sampling/stack_collector.pyi: removed re-export of get_combined_css —
  same reason as above
- sampling/sample.pyi: removed re-export of fmt — private formatting
  helper leaked into a public module's stub

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: johnslavik

stdlib/profiling/sampling/_child_monitor.pyi

@@ -2,9 +2,6 @@ import types
 from typing import Any
 from typing_extensions import Self
 
-def get_child_pids(pid: int, recursive: bool = True) -> list[int]: ...
-def is_python_process(pid: int) -> bool: ...
-
 class ChildProcessMonitor:
     parent_pid: int
     cli_args: list[str]

stdlib/profiling/sampling/_css_utils.pyi

@@ -3,8 +3,6 @@ from collections import Counter
 from dataclasses import dataclass
 from typing import Any
 
-from ._css_utils import get_combined_css as get_combined_css
-from ._format_utils import fmt as fmt
 from .collector import extract_lineno as extract_lineno, normalize_location as normalize_location
 from .opcode_utils import format_opcode as format_opcode, get_opcode_info as get_opcode_info
 from .stack_collector import StackTraceCollector as StackTraceCollector

stdlib/profiling/sampling/_format_utils.pyi

@@ -1,7 +1,6 @@
 from _typeshed import Incomplete
 from collections import deque
 
-from ._format_utils import fmt as fmt
 from .binary_collector import BinaryCollector as BinaryCollector
 from .collector import Collector as Collector
 from .constants import (

stdlib/profiling/sampling/_sync_coordinator.pyi

@@ -3,7 +3,6 @@ from _typeshed import StrOrBytesPath
 from collections import Counter
 from typing import Any
 
-from ._css_utils import get_combined_css as get_combined_css
 from .collector import Collector as Collector, extract_lineno as extract_lineno
 from .opcode_utils import get_opcode_mapping as get_opcode_mapping
 from .string_table import StringTable as StringTable