feat(dpu): DPU out of order streaming replacement based html end stamp

[MaxwellCohen]

This is an alternative DPU template for streaming using an HTML end-stamp comment to let the mutation observer know when to run replacement code. This approach is more targeted and, in theory, more reliable than #474 for race conditions or edge cases, at the cost of slightly more HTML for each boundary of about 9 bytes per resolved suspence boundary resulting in a this sending more html at about 8 boundaries.

Metric	main	branch	Δ
INIT_SCRIPT body	1135	1066	−69
createInitScript() tag	1168	1099	−69
createSubtree()	69	55	−14
Suspense fallback wrapper	33	56	+23
One boundary stamp overhead	77	86	+9
First suspend total (stamps + init)	1245	1185	−60

code sand box link to use this PR can be seen here
https://ci.codesandbox.io/status/MaxwellCohen/preact-render-to-string/pr/6/builds/691802

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Latest commit: 9e6e8b1

The changes in this PR will be included in the next version bump.

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Name	Type
preact-render-to-string	Minor

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