[Php85] Deprecate NestedFuncCallsToPipeOperatorRector and SequentialAssignmentsToPipeOperatorRector

[TomasVotruba]

Deprecates both pipe-operator rules.

Both rules take working code and rewrite it into a |> chain. Whether that is an improvement depends entirely on the surrounding code, so it cannot be decided mechanically:

• Extremely long chains — nothing bounds the chain length, so a deeply nested expression turns into a wall of pipes that is harder to read than what it replaced.
• Opinionated boundary — the point where "readable pipe" becomes "too much" is a personal preference. NestedFuncCallsToPipeOperatorRector even exposes it as a minimum_depth option, which is the tell that there is no correct default.
• The convert-all-calls flow is broken, waits for PHP 8.6 partial function https://amitmerchant.com/partial-function-application-php-86/
• Lost variables — SequentialAssignmentsToPipeOperatorRector deletes the intermediate variables. Those names document what each step produces, and they may be re-used later.

If needed, implement as custom rule with your specific boundaries and needs.

NestedFuncCallsToPipeOperatorRector

-$result = trim(strtolower(htmlspecialchars($input)));
+$result = $input
+    |> htmlspecialchars(...)
+    |> strtolower(...)
+    |> trim(...);

Neither rule was registered in any set, so nothing is removed from `php85.php` or the levels. Rules now implement `DeprecatedInterface`, `refactor()` throws, and their tests are dropped — same shape as #8283.