feat: warn for lowercase object.component rendering

[paoloricciuti]

Svelte 5 rewrite

As discussed in #12694 i've reverted the warn for lowercase object.component in that pr and i'm opening this one to continue discussing what we should do.

The options are:

1. warn like this pr is doing
2. consider object.component a component and not a RegularElement...this could be technically problematic for Svelte Native so we are waiting for a word from @halfnelson on it (you can follow the discussion starting from here

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[Rich-Harris]

merged #12798, so I'll close this — thanks

[paoloricciuti]

merged #12798, so I'll close this — thanks

Sure, much better honestly...did we also got an answer from Svelte Native side?

[Rich-Harris]

no, but I'm confident that it's solvable