Document compiler diagnostics related to the default constraing

[BillWagner]

Fixes #53547

Add the diagnostic codes fro the default constraint. In addition, sweep for other errors and warnings related to generic constraints.

Clean up existing related files, and add other related (but undocumented) diagnostics.

Because this added quite a few errors codes, the main file got a substantial rewrite and reorganization.

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Internal previews

📄 File	🔗 Preview link
docs/csharp/language-reference/compiler-messages/generic-type-parameters-errors.md	Resolve errors and warnings related to generic type parameters and generic type arguments
docs/csharp/language-reference/toc.yml	docs/csharp/language-reference/toc
docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md	Coming in C# 15
docs/csharp/programming-guide/generics/generic-methods.md	"Generic Methods"

[Copilot]

Pull request overview

This PR updates the C# compiler-diagnostics documentation by consolidating many generic-constraint-related diagnostics (including the C# 9 default constraint diagnostics) into the existing “generic type parameters and type arguments” hub page, and removing older per-diagnostic pages in favor of redirects.

Changes:

• Expanded and reorganized generic-type-parameters-errors.md to include additional generic constraint diagnostics (including default constraint diagnostics) and related guidance.
• Removed multiple docs/csharp/misc/cs*.md diagnostic pages (and cs1763.md) that are now covered by the consolidated hub page.
• Updated C# language reference TOC entries and added redirects so old URLs continue to resolve.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md	Removes diagnostics that are now documented elsewhere from the “undocumented errors” keyword list.
docs/csharp/misc/cs3024.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs1948.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs1720.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0718.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0704.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0701.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0699.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0693.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0456.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0453.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0452.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0411.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0409.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/misc/cs0406.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
docs/csharp/language-reference/toc.yml	Updates the TOC’s generic diagnostics entry keywords and removes TOC entries for deleted per-diagnostic pages.
docs/csharp/language-reference/compiler-messages/generic-type-parameters-errors.md	Major rewrite/reorganization to document additional generic constraints diagnostics (including default constraint).
docs/csharp/language-reference/compiler-messages/cs1763.md	Deleted; content is now covered by the consolidated generic diagnostics page (with redirect).
.openpublishing.redirection.csharp.json	Adds redirects from removed diagnostic pages to the consolidated generic diagnostics page.

Comments suppressed due to low confidence (1)

docs/csharp/language-reference/compiler-messages/generic-type-parameters-errors.md:166

• CS0312/CS0313 message text differs between the top diagnostic list and the later section (the summary repeats the 'type1' placeholder in the second sentence, but the detailed section doesn’t). Align the wording so readers (and search engines) see one consistent message form for each diagnostic.

- [**CS0312**](#constraint-satisfaction-and-conversions): *The type 'type1' cannot be used as type parameter in the generic type or method. The nullable type 'type1' does not satisfy the constraint of 'constraint'.*
- [**CS0313**](#constraint-satisfaction-and-conversions): *The type 'type1' cannot be used as type parameter in the generic type or method. The nullable type 'type1' does not satisfy the constraint of 'constraint'. Nullable types can not satisfy any interface constraints.*
- [**CS0314**](#constraint-satisfaction-and-conversions): *The type cannot be used as type parameter in the generic type or method. There is no boxing conversion or type parameter conversion from 'type' to 'constraint'.*