Deprecate std::filesystem namespace include

Clang-tidy is complaining about our using fs = ... directives.  These
were originally added to handle boost::filesystem vs
std::experimental::filesystem vs std::filesystem between the various
compilers.  Now that we're all on std::filesystem, this redefinition can
be removed.

```
ChassisIntrusionSensor.hpp:11:11: error: namespace alias decl 'fs' is unused [misc-unused-alias-decls,-warnings-as-errors]
   11 | namespace fs = std::filesystem;
```

Tested: code compiles

Change-Id: If4b968ff9cceb4038f526321d3c7c11563ffbce9
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/src/DeviceMgmt.cpp b/src/DeviceMgmt.cpp
index 6d6c296..f36b68a 100644
--- a/src/DeviceMgmt.cpp
+++ b/src/DeviceMgmt.cpp
@@ -15,8 +15,6 @@
 #include <system_error>
 #include <variant>
 
-namespace fs = std::filesystem;
-
 std::optional<I2CDeviceParams> getI2CDeviceParams(
     const I2CDeviceTypeMap& dtmap, const SensorBaseConfigMap& cfg)
 {
@@ -47,7 +45,7 @@
     return I2CDeviceParams(findDevType->second, *bus, *addr);
 }
 
-static fs::path i2cBusPath(uint64_t bus)
+static std::filesystem::path i2cBusPath(uint64_t bus)
 {
     return {"/sys/bus/i2c/devices/i2c-" + std::to_string(bus)};
 }
@@ -62,7 +60,7 @@
 
 bool I2CDeviceParams::devicePresent() const
 {
-    fs::path path = i2cBusPath(bus) / deviceDirName(bus, address);
+    std::filesystem::path path = i2cBusPath(bus) / deviceDirName(bus, address);
 
     if (type->createsHWMon)
     {
@@ -71,7 +69,7 @@
 
     // Ignore errors; anything but a clean 'true' is fine as 'false'
     std::error_code ec;
-    return fs::exists(path, ec);
+    return std::filesystem::exists(path, ec);
 }
 
 bool I2CDeviceParams::deviceStatic() const
@@ -81,12 +79,13 @@
         return false;
     }
 
-    fs::path ofNode = i2cBusPath(bus) / deviceDirName(bus, address) / "of_node";
+    std::filesystem::path ofNode =
+        i2cBusPath(bus) / deviceDirName(bus, address) / "of_node";
 
     // Ignore errors -- if of_node is present the device is a static DT node;
     // otherwise we can assume we created it from userspace.
     std::error_code ec;
-    return fs::exists(ofNode, ec);
+    return std::filesystem::exists(ofNode, ec);
 }
 
 I2CDevice::I2CDevice(I2CDeviceParams params) : params(params)
@@ -111,7 +110,7 @@
     }
 
     // Try to create it: 'echo $devtype $addr > .../i2c-$bus/new_device'
-    fs::path ctorPath = i2cBusPath(params.bus) / "new_device";
+    std::filesystem::path ctorPath = i2cBusPath(params.bus) / "new_device";
     std::ofstream ctor(ctorPath);
     if (!ctor.good())
     {
@@ -144,7 +143,7 @@
     // partially successful (i.e. when params.devicePresent() would return
     // false but there's still a dummy i2c client device to remove)
 
-    fs::path dtorPath = i2cBusPath(params.bus) / "delete_device";
+    std::filesystem::path dtorPath = i2cBusPath(params.bus) / "delete_device";
     std::ofstream dtor(dtorPath);
     if (!dtor.good())
     {