Support encoding TypedReferences in signatures.

[teo-tsirpanis]

This PR does two things. It adds a SignatureTypeEncoder.TypedReference() method and updates the SignatureTypeEncoder.PrimitiveType method to accept values of PrimitiveTypeCode.TypedReference. Any of the two ways allows encoding a typed reference with System.Reflection.Metadata.

Fixes #80812. Tests were updated.

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This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

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Issue Details

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This PR does two things. It adds a SignatureTypeEncoder.TypedReference() method and updates the SignatureTypeEncoder.PrimitiveType method to accept values of PrimitiveTypeCode.TypedReference. Any of the two ways allows encoding a typed reference with System.Reflection.Metadata.

Fixes #80812. Tests were updated.

Author:	teo-tsirpanis
Assignees:	-
Labels:	area-System.Reflection.Metadata, new-api-needs-documentation
Milestone:	-

[buyaa-n]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

@teo-tsirpanis please add doc with triple slash comment for the, even all other similar APIs have not documented we should keep documenting the new ones at least. Other than that the PR looks good to me, thank you!

[teo-tsirpanis]

Done @buyaa-n, I documented the entire SignatureTypeEncoder and reworded some of the existing documentation.

[buyaa-n]

LGTM, thanks you @teo-tsirpanis