Add lossy flag in CastOptions

[klion26]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

As discussed in #8873, we need to add a field lossy in CastOptions, so that we can support lossy cast in the variant-get(#8982 ), as this will add a field in the pub struct, so we need to add this in a major version.

Describe the solution you'd like

Add a field lossy in CastOptions and change the usages.

Describe alternatives you've considered

Additional context

[klion26]

take

[klion26]

The cast kernel treats lossy = true(without the flag) from introducing this cast logic(2019), we'll keep it as now, so close this one. We can improve the logic in variant_get according to the logic in the cast kernel.