feat(etag): allow for custom hashing methods to be used to etag #6212

Job	Run time
Fastly Compute	49s
Bun	12s
Deno	16s
Checking if it's valid for JSR	9s
AWS Lambda	46s
Lambda@Edge	50s
Main	1m 48s
Node.js v18.18.2	49s
Type & Bundle size Check on Main	0s
Node.js v20.x	46s
Type & Bundle size Check on PR	59s
Node.js v22.x	46s
workerd	53s
Coverage	8s
	9m 11s

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