fix: properly calculate content-length for cfn custom resource responses

[auvred]

Ref: aws/aws-cdk#24501

Custom Resources need to write their response into a S3 object.
This is implemented as a PUT request to a pre-signed URL and has to specify the content-length of the response object.
Previously the CustomResource code would use responseBody.length.
However this returns the number of graphemes, not bytes.
If any utf8 characters with graphemes != bytes are part of the response, CloudFormation would fail the deployment with a Response is not valid JSON error.

[changeset-bot]

🦋 Changeset detected

Latest commit: f1d7b9a

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

This PR includes changesets to release 6 packages

Name	Type
sst	Patch
@sst/console	Patch
create-sst	Patch
astro-sst	Patch
svelte-kit-sst	Patch
solid-start-sst	Patch

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[jayair]

Oh interesting. Let me ask the team to take a look.