Extend JsonIncludeAttribute and JsonConstructorAttribute support to internal and private members

[eiriktsarpalis]

The JsonInclude and JsonConstructor attributes are annotations that can be applied directly to individual members to include them in the JSON contract for a specific type. Historically however these attributes haved either:

1. only worked on public members (JsonConstructor),
2. applied arbitrary restrictions for the attribute to have effect (e.g. JsonInclude on properties requires that either the getter or setter should be public for the non-public counterpart to be accessed) or,
3. applied inconsistently depending on whether the member is a property or a field (JsonInclude).

This PR changes the semantics of both attributes so that they have uniform behavior regardless of accessibility. It assumes that users know what they're doing when annotating a given member and tries to accommodate their request. A notable exception to this rule is the source generator, which will warn/throw a runtime exception if the user tries to include members that are not accessible to the source generated context.

Fix #87431

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Issue Details

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The JsonInclude and JsonConstructor attributes are annotations that can be applied directly to individual members to include them in the JSON contract for a specific type. Historically however these attributes haved either:

1. only worked on public members (JsonConstructor),
2. applied arbitrary restrictions for the attribute to have effect (e.g. JsonInclude on properties requires that either the getter or setter should be public for the non-public counterpart to be accessed) or,
3. applied inconsistently depending on whether the member is a property or a field (JsonInclude).

This PR changes the semantics of both attributes so that they have uniform behavior regardless of accessibility. It assumes that users know what they're doing when annotating a given member and tries to accommodate their request. A notable exception to this rule is the source generator, which will warn/throw a runtime exception if the user tries to include members that are not accessible to the source generated context.

Fix #87431

Author:	eiriktsarpalis
Assignees:	eiriktsarpalis
Labels:	area-System.Text.Json
Milestone:	-

[jeffhandley]

A notable exception to this rule is the source generator, which will warn/throw a runtime exception if the user tries to include members that are not accessible to the source generated context.

Is this an application-runtime exception, or is this a source-generator-runtime exception / application-design-time build error?

[eiriktsarpalis]

A notable exception to this rule is the source generator, which will warn/throw a runtime exception if the user tries to include members that are not accessible to the source generated context.

Is this an application-runtime exception, or is this a source-generator-runtime exception / application-design-time build error?

It's both -- a diagnostic warning will be emitted at compile time and an exception will be thrown at run time.

[eiriktsarpalis]

Test failures are unrelated and tracked by #88453