Override same attributes found at class and property level in ApplicationSettingsBase

[buyaa-n]

Fixes #62593

Looks by the design when the existing attribute is found at property level it should override the class level attribute, but the code is not really overriding,

runtime/src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/ApplicationSettingsBase.cs

Lines 518 to 522 in 89857ea

	// NOTE: The key is the type. So if an attribute was found at class
	// level and also property level, the latter overrides the former
	// for a given setting. This is exactly the behavior we want.
	settingsProperty.Attributes.Add(attribute.GetType(), attribute);

The bug found with nullable attributes added by compiler

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Issue Details

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Fixes #62593

Looks by the design when the existing attribute is found at property level it should override the class level attribute, but the code is not really overriding,

runtime/src/libraries/System.Configuration.ConfigurationManager/src/System/Configuration/ApplicationSettingsBase.cs

Lines 518 to 522 in 89857ea

	// NOTE: The key is the type. So if an attribute was found at class
	// level and also property level, the latter overrides the former
	// for a given setting. This is exactly the behavior we want.
	settingsProperty.Attributes.Add(attribute.GetType(), attribute);

The bug found with nullable attributes added by compiler

Author:	buyaa-n
Assignees:	-
Labels:	area-System.Configuration
Milestone:	7.0.0