Corrected DataTable deserialization to use invariant culture for schema properties (#26298)

* Updated schema property processing in the XMLSchema and XSDSchema types in XMLSchema.cs.
Added unit tests to verify that culture settings are ignored both in serialization and deserialization of XML schemas, as employed by the serialization of DataTable objects.

* Updated the XsdSchemaDeserializationIgnoresLocale test to be skipped on the full framework, and added test XsdSchemaDeserializationOnFullFrameworkStillHasBug to only run on the full framework to ensure we get alerted when the full framework does get the fix, so that the main test can be re-enabled there.

* Updated DataTableReadXmlSchemaTest.cs to run the XsdSchemaSerializationIgnoresLocale and XsdSchemaDeserializationIgnoresLocale tests, which modify the current culture, out-of-process using RemoteExecutorTestBase. (The XsdSchemaDeserializationOnFullFrameworkStillHasBug still runs in-process, as that test only runs on the full framework anyway.)

* Applied code style recommendations from @ViktorHofer.
Corrected the XsdSchemaDeserializationOnFullFrameworkStillHasBug test to restore the culture after verifying the exception.

Author: logiclrd

src/System.Data.Common/src/System/Data/XMLSchema.cs

@@ -47,7 +47,7 @@ internal static void SetProperties(object instance, XmlAttributeCollection attrs
                         object propValue;
                         if (converter.CanConvertFrom(typeof(string)))
                         {
-                            propValue = converter.ConvertFromString(value);
+                            propValue = converter.ConvertFromInvariantString(value);
                         }
                         else if (type == typeof(Type))
                         {
@@ -298,7 +298,7 @@ internal static void SetProperties(object instance, XmlAttribute[] attrs)
                         object propValue;
                         if (converter.CanConvertFrom(typeof(string)))
                         {
-                            propValue = converter.ConvertFromString(value);
+                            propValue = converter.ConvertFromInvariantString(value);
                         }
                         else if (type == typeof(Type))
                         {