fix(database): fix is relation loaded and correctly unset properties

[laylatichy]

unset property so lazy loading works correctly for belongstoman, isRelationLoaded returns corect value and empty results are correctly set

[github-actions]

Benchmark Results

Comparison of feat/unset-default-belongs-to-many-relations against 3.x (3d5833ee0dc13c60845bb421f5cb72e3ac9b1452).

Open to see the benchmark results

Benchmark	Set	Mem. Peak	Time	Variability
ViewRenderBench(benchExpressions)	-	24.513mb 0.00%	545.292μs +5.38%	±1.08% -58.19%

_{Generated by phpbench against commit e733691}

[laylatichy]

@brendt some fixes so isRelationLoaded works correctly

but, it might have breaking behavior, kinda I guess if somebody relied on broken behavior in his app to work

now

class Author {
    public ?Publisher $publisher = null
}

isrelationloaded false, author->publisher throws relationmissing if we dont ->load('publisher') before

class Author {
    #[Lazy]
    public ?Publisher $publisher = null
}

isrelationloaded false, author->publisher loads data

class Author {
    #[Eager]
    public ?Publisher $publisher = null
}

isrelationloaded true, author->publisher shows data loaded at the time of author fetch

I guess thats how it should work?