Add docs for diagnostics related to tuple declarations

[BillWagner]

Fixes #55337

Add all diagnostic codes related to tuple declarations and use. These were added in C# 7.x

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Internal previews

File	Preview link
.openpublishing.redirection.csharp.json	Preview published page
docs/csharp/language-reference/compiler-messages/tuple-errors.md	Preview published page
docs/csharp/language-reference/toc.yml	Preview published page
docs/csharp/misc/sorry-we-don-t-have-specifics-on-this-csharp-error.md	Preview published page

[Copilot]

Pull request overview

This pull request adds a consolidated documentation page for C# tuple-related diagnostics (tuple element names, metadata, conversions, equality, type inference, and tuple-related pattern matching), and updates navigation and redirects so older per-diagnostic pages continue to resolve correctly.

Changes:

• Added a new Tuple declarations compiler-messages page that documents the tuple-themed diagnostics in one place.
• Updated the C# language reference TOC and removed individual TOC entries for diagnostics that are now covered by the consolidated page.
• Added redirects for removed per-diagnostic pages, and removed those diagnostics from the “sorry we don’t have specifics” catch-all page.

Reviewed changes

Copilot reviewed 11 out of 11 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 tuple-related diagnostic codes that are now documented elsewhere.
docs/csharp/language-reference/toc.yml	Adds a “Tuple declarations” node pointing to the new consolidated article, and removes individual TOC entries now covered by it.
docs/csharp/language-reference/compiler-messages/tuple-errors.md	New consolidated documentation page for tuple-related compiler errors and warnings.
docs/csharp/language-reference/compiler-messages/cs8210.md	Removes the standalone CS8210 page (now covered by tuple-errors.md via redirect).
docs/csharp/language-reference/compiler-messages/cs8141.md	Removes the standalone CS8141 page (now covered by tuple-errors.md via redirect).
docs/csharp/language-reference/compiler-messages/cs8140.md	Removes the standalone CS8140 page (now covered by tuple-errors.md via redirect).
docs/csharp/language-reference/compiler-messages/cs8139.md	Removes the standalone CS8139 page (now covered by tuple-errors.md via redirect).
docs/csharp/language-reference/compiler-messages/cs8127.md	Removes the standalone CS8127 page (now covered by tuple-errors.md via redirect).
docs/csharp/language-reference/compiler-messages/cs8125.md	Removes the standalone CS8125 page (now covered by tuple-errors.md via redirect).
docs/csharp/language-reference/compiler-messages/cs8124.md	Removes the standalone CS8124 page (now covered by tuple-errors.md via redirect).
.openpublishing.redirection.csharp.json	Adds redirects from removed per-diagnostic pages to the new consolidated tuple diagnostics page.

Suppressed comments (1)

docs/csharp/language-reference/compiler-messages/tuple-errors.md:111

• The CS8179 message is missing a trailing period in the "ValueTuple infrastructure" section, but the same message includes a period in the earlier list at the top of the article. Make the punctuation consistent.

- **CS8128**: *Member 'member' was not found on type 'type' from assembly 'assembly'.*
- **CS8179**: *Predefined type 'type' is not defined or imported*
- **CS8182**: *Predefined type 'type' must be a struct.*

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