deconflict inline component instance variable name

[Conduitry]

Fixes #4636.

[Conduitry]

Marking this as draft. The failing js sample tests made me notice that this is apparently being a bit overzealous with the deconflicting and I want to take another look at why that's happening.

[tanhauhau]

wonder you get any findings on this one.
from what i gather, get_unique_name is called twice, that's why.

• after all the render_dom wrappers were created, each of their variable name is not yet deconflicted. after that, the Renderer will call assign_variable_name to call get_unique_name to deconflict them.

but your change calls the get_unique_name in the InlineComponentWrappers constructor as well.

calling the get_unique_name first, will add the variable name into the set, and calling it again with the same name will deconflict it, causing the name to change, even though there's no naming conflict.

i wonder maybe we should do deconflict in each wrapper, instead of inside the assign_variable_name? i see a // TODO messy over there.

i hv a working branch, https://github.com/sveltejs/svelte/compare/master...tanhauhau:tanhauhau/deconflict-wrapper-var-names?expand=1, that i haven't updated the sample test.

but doing so, the generated variable name is very messy, attached 1 updated sample test in the diff.