Add ConditionalPaths type

[naman-luthra-rubrik]

This PR:

• Adds ConditionalPaths<Type, Condition, Options> - the path-aware counterpart of ConditionalKeys. Returns a union of all dot-notation paths in an object whose value type satisfies Condition.
• Closes Proposal: ConditionalPaths #1328

Supports:

• extends mode (default): value assignable to Condition
• equality mode: exact type match via IsEqual
• All Paths options except leavesOnly (which is a no-op for any specific-type condition since primitive-typed fields are always leaves)

[sindresorhus]

This is described as the path-aware counterpart of ConditionalKeys, but the semantics differ. Optional properties are treated as required before checking the condition, so {name?: string} filtered by string includes name. ConditionalKeys requires string | undefined for that.

never properties also match evry condition because of the tuple-wrapped extends check, so {data: never; name: string} filtered by string includes both paths. That is suprising, and ConditionalKeys already avoids this with ExtendsStrict.

I'm also not convinced the new type is worth duplicating most of the path-generation logic. If we add this, I think it should be a thin composition over Paths, Get, and ExtendsStrict, unless there is a benchmark showing that approach is too slow.

I feel like this is a bit too niche