remove getters

[Rich-Harris]

Closes #6199
Closes #6126

Something we noticed recently is that our use of accessors on RequestEvent and LoadEvent made it difficult to do this sort of thing:

const augmented_event = { ...event, extra_stuff };

On RequestEvent, we had get clientAddress — this PR changes that to getClientAddress, which is a breaking change.

On LoadEvent, we previously had get url. But we don't actually need to track whether url was accessed, just whether its properties were accessed (and only the properties that could change during a session — not url.origin etc), allowing load functions to be more conservative about when they re-run.

I also noticed we weren't previously tracking url access when loading server data, which is now fixed.

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Latest commit: cd4bbc8

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@sveltejs/kit	Patch

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[dummdidumm]

Looks good except for one minor detail which could be cleaned up