Remove duplicate equality operator for QgsPointXY

We had two different(!!!!) implementations for equality operator
for QgsPointXY, with different logic (one handled empty points,
the other didn't). This compiled only because one was not marked
as const. So we'd get a DIFFERENT equality check logic depending
on whether or not the first point was const... eeek!

Remove the duplicate one, mark the better one as const

Author: nyalldawson

python/PyQt6/core/auto_generated/qgspointxy.sip.in

@@ -220,7 +220,7 @@ Compares this point with another point with a fuzzy tolerance using distance com
 .. versionadded:: 3.36
 %End
 
-    bool operator==( const QgsPointXY &other ) /HoldGIL/;
+    bool operator==( const QgsPointXY &other ) const /HoldGIL/;
 
     bool operator!=( const QgsPointXY &other ) const /HoldGIL/;
 
@@ -290,7 +290,6 @@ Multiply x and y by the given value
 
 
 
-
 /************************************************************************
  * This file has been generated automatically from                      *
  *                                                                      *

python/core/auto_generated/qgspointxy.sip.in

@@ -220,7 +220,7 @@ Compares this point with another point with a fuzzy tolerance using distance com
 .. versionadded:: 3.36
 %End
 
-    bool operator==( const QgsPointXY &other ) /HoldGIL/;
+    bool operator==( const QgsPointXY &other ) const /HoldGIL/;
 
     bool operator!=( const QgsPointXY &other ) const /HoldGIL/;
 
@@ -290,7 +290,6 @@ Multiply x and y by the given value
 
 
 
-
 /************************************************************************
  * This file has been generated automatically from                      *
  *                                                                      *

src/core/qgspointxy.h

@@ -270,7 +270,7 @@ class CORE_EXPORT QgsPointXY
       return QgsGeometryUtilsBase::fuzzyDistanceEqual( epsilon, mX, mY, other.x(), other.y() );
     }
 
-    bool operator==( const QgsPointXY &other ) SIP_HOLDGIL
+    bool operator==( const QgsPointXY &other ) const SIP_HOLDGIL
     {
       if ( isEmpty() && other.isEmpty() )
         return true;
@@ -399,26 +399,6 @@ class CORE_EXPORT QgsPointXY
 
 Q_DECLARE_METATYPE( QgsPointXY )
 
-inline bool operator==( const QgsPointXY &p1, const QgsPointXY &p2 ) SIP_SKIP
-{
-  const bool nan1X = std::isnan( p1.x() );
-  const bool nan2X = std::isnan( p2.x() );
-  if ( nan1X != nan2X )
-    return false;
-  if ( !nan1X && !qgsDoubleNear( p1.x(), p2.x(), 1E-8 ) )
-    return false;
-
-  const bool nan1Y = std::isnan( p1.y() );
-  const bool nan2Y = std::isnan( p2.y() );
-  if ( nan1Y != nan2Y )
-    return false;
-
-  if ( !nan1Y && !qgsDoubleNear( p1.y(), p2.y(), 1E-8 ) )
-    return false;
-
-  return true;
-}
-
 inline std::ostream &operator << ( std::ostream &os, const QgsPointXY &p ) SIP_SKIP
 {
   // Use Local8Bit for printouts