[esp32_ble] Reference count BLE advertising

Advertising was started when the BLE server came up and never stopped, so a
device that auto-loads esp32_ble_server for esp32_improv advertised over BLE
forever - even with WiFi connected and Improv never started.

Components now request advertising with advertising_start() and release it
with advertising_stop(); the radio only advertises while at least one request
is held. The BLE server only requests it when the configuration defines
services or manufacturer data of its own, Improv holds a request for as long
as provisioning is possible, and a beacon holds one permanently.

Fixes https://github.com/esphome/esphome/issues/18938

tests/component_tests/esp32_ble_server/config/improv_only.yaml

@@ -0,0 +1,13 @@
+esphome:
+  name: test
+
+esp32:
+  variant: esp32
+
+wifi:
+  ssid: MySSID
+  password: password1
+
+# esp32_ble_server is only auto-loaded here, so it has no services of its own.
+esp32_improv:
+  authorizer: none

tests/component_tests/esp32_ble_server/config/manufacturer_data_only.yaml

@@ -0,0 +1,9 @@
+esphome:
+  name: test
+
+esp32:
+  variant: esp32
+
+esp32_ble_server:
+  id: ble_server
+  manufacturer_data: [0x72, 0x04, 0x00, 0x23]

tests/component_tests/esp32_ble_server/config/own_service.yaml

@@ -0,0 +1,14 @@
+esphome:
+  name: test
+
+esp32:
+  variant: esp32
+
+esp32_ble_server:
+  id: ble_server
+  services:
+    - uuid: 2a24b789-7aab-4535-af3e-ee76a35cc12d
+      characteristics:
+        - uuid: cad48e28-7fbe-41cf-bae9-d77a6c233423
+          read: true
+          value: [1, 2, 3, 4]

tests/component_tests/esp32_ble_server/test_esp32_ble_server.py

@@ -1,5 +1,10 @@
 """Tests for esp32_ble_server configuration helpers."""
 
+from __future__ import annotations
+
+from collections.abc import Callable
+from pathlib import Path
+
 import pytest
 
 from esphome.components.esp32_ble_server import (
@@ -45,3 +50,26 @@ def test_uuid_is_matches_descriptor_short_strings(uuid16) -> None:
     assert uuid_is(uuid16, uuid16)
     assert uuid_is(f"{uuid16:04X}", uuid16)
     assert uuid_is(f"{uuid16:08X}", uuid16)
+
+
+@pytest.mark.parametrize(
+    ("config_file", "required"),
+    [
+        # Auto-loaded by esp32_improv only: nothing to find until Improv asks for it
+        ("improv_only.yaml", False),
+        # The configuration defines a service clients are meant to connect to
+        ("own_service.yaml", True),
+        # Manufacturer data is only useful if it is actually broadcast
+        ("manufacturer_data_only.yaml", True),
+    ],
+)
+def test_advertising_required(
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+    config_file: str,
+    required: bool,
+) -> None:
+    """The server only requests advertising when the configuration needs it."""
+    main_cpp = generate_main(component_config_path(config_file))
+
+    assert f"set_advertising_required({str(required).lower()})" in main_cpp