[CodingStyle] Deprecate NestedTernaryToMatchRector

[TomasVotruba]

NestedTernaryToMatchRector is not part of any set - it only runs when registered by hand.

Beyond that, the output is rarely an improvement. match (true) over nested conditions reads as a lookup table while it is really a chain of unrelated boolean tests, so the intent gets less obvious, not more:

-$value = $input > 100 ? 'more than 100' : ($input > 5 ? 'more than 5' : 'less');
+$value = match (true) {
+    $input > 100 => 'more than 100',
+    $input > 5 => 'more than 5',
+    default => 'less',
+};

Both versions hide the same problem. The useful refactoring is explicit intent - early returns or a named method - which no rule can decide for you.

Standard deprecation shape: implements DeprecatedInterface, refactor() throws, tests removed. The ConditionAndResult value object goes with it, it had no other use.