[CodeQuality] Add ExplicitNullableObjectInstanceRector, deprecate 4 nullable-object instanceof rules

[TomasVotruba]

Merges four rules that all rewrite an implicit nullable-object check into an explicit instanceof, into a single ExplicitNullableObjectInstanceRector. Each old rule only differed in the input idiom; the output and the underlying factory are the same.

Merged (now deprecated, kept as throwing stubs for BC):

• ObjectExplicitBoolCompareRector - !$item / $item
• FlipTypeControlToUseExclusiveTypeRector - $item === null / !== null
• EmptyOnNullableObjectToInstanceOfRector - empty($item) / !empty($item)
• WhileNullableToInstanceofRector - while ($item !== null) / while ($item)

All four produce $item instanceof X (negated as needed) via the shared NullableObjectToInstanceofFactory. The new rule subscribes to the union of their node types and dispatches by node, keeping each original detection and type-resolution path intact.

BinaryOpNullableToInstanceofRector (&& / ||) stays separate as requested.

The rule is registered in CodeQualityLevel; the two old entries there and the two in TypeDeclarationLevel are removed. Two tests/Issues configs that pinned the old rules by class-string are repointed to the new rule.

Fixtures cover every idiom (truthiness, null compare, empty, while/do-while) plus a nullable-scalar skip. Full suite green locally.

[TomasVotruba]

These 4 rules do basically the same operation, nullable object + weak condition around it →instanceof check 👍
You want them all or none. This will speed up the process a bit and streamline its usage.

[parijke]

@TomasVotruba I already found this in the public docs, but it isn't released yet?

[TomasVotruba]

That's because website deploys regularly with latest version to allow demo testing 👍

[parijke]

That's because website deploys regularly with latest version to allow demo testing 👍

Good to know!