Fix R2 tracing to use unique tags for each checksum type instead of overwriting shared tags

[mar-cf]

No description provided.

[jmorrell-cloudflare]

I don't think multiple checksums are allowed: https://developers.cloudflare.com/r2/api/workers/workers-api-reference/#r2putoptions

Note
Only a single hashing algorithm can be specified at once.

That said, this would be better if we ever relaxed that requirement in the future. However I think it's harder to query, so I'm a little torn.

[mar-cf]

Alternatively, we could just set the first seen checked in a preset order.

And/or post under a different tag, checksum2 or something along those lines.

Only a single hashing algorithm can be specified at once.

That may be true, but I noticed that doesn't hold all the time.

@jmorrell-cloudflare LMK what you prefer