Standardize pattern used for property comments

[captainsafia]

Closes #63201.

• If <summary> is the only tag on a property, it is set as the description.
• If both <summary> and <value> are on a property, then they are both set in the description as {summary}\n{value}
• If only <value> is set, it is set as the description.
• <returns> is ignored since it doesn't make sense to have on a property and its clearer if we only repect it on methods.

[Copilot]

Pull Request Overview

This PR standardizes how XML documentation comments are processed for properties in OpenAPI generation. The change implements a new priority system where both <summary> and <value> tags are combined in property descriptions, while <returns> tags are ignored for properties since they don't make semantic sense.

• Implements new logic to combine <summary> and <value> tags with newline separation
• Ignores <returns> tags on properties since they're not semantically appropriate
• Updates all test snapshots to reflect the new combined description format

Reviewed Changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

File	Description
XmlCommentGenerator.Emitter.cs	Core implementation of the new property comment standardization logic
Various test snapshot files	Updated to reflect new combined description format with summary and value
Test files (SchemaTests.cs, OperationTests.MinimalApis.cs, CompletenessTests.cs, AdditionalTextsTests.Schemas.cs)	Added comprehensive test cases and updated assertions for the new behavior