Revert #724e1a7 and replace with stack checks.

Replaces `NimBLEDevice::setConnectionInProgress` and `NimBLEDevice::isConnectionInProgress()` with lower level checks to avoid potential incorrect state reporting.
`NimBLEClient::connect` will instead call `NimBLEScan::stop` if it stopped the scan to release any resources waiting, the call the callback if set.

src/NimBLEDevice.cpp

@@ -101,10 +101,6 @@ std::vector<NimBLEAddress> NimBLEDevice::m_ignoreList{};
 std::vector<NimBLEAddress> NimBLEDevice::m_whiteList{};
 uint8_t                    NimBLEDevice::m_ownAddrType{BLE_OWN_ADDR_PUBLIC};
 
-# if defined(CONFIG_BT_NIMBLE_ROLE_CENTRAL) || defined(CONFIG_BT_NIMBLE_ROLE_PERIPHERAL)
-bool NimBLEDevice::m_connectionInProgress{false};
-# endif
-
 # ifdef ESP_PLATFORM
 #  ifdef CONFIG_BTDM_BLE_SCAN_DUPL
 uint16_t NimBLEDevice::m_scanDuplicateSize{CONFIG_BTDM_SCAN_DUPL_CACHE_SIZE};
@@ -1238,23 +1234,6 @@ bool NimBLEDevice::setCustomGapHandler(gap_event_handler handler) {
     return rc == 0;
 } // setCustomGapHandler
 
-/**
- * @brief Set the connection in progress flag.
- * @param [in] inProgress The connection in progress flag.
- * @details This is used to prevent a scan from starting while a connection is in progress.
- */
-void NimBLEDevice::setConnectionInProgress(bool inProgress) {
-    m_connectionInProgress = inProgress;
-} // setConnectionInProgress
-
-/**
- * @brief Check if a connection is in progress.
- * @return True if a connection is in progress.
- */
-bool NimBLEDevice::isConnectionInProgress() {
-    return m_connectionInProgress;
-} // isConnectionInProgress
-
 /**
  * @brief Return a string representation of the address of this device.
  * @return A string representation of this device address.