Limit GraphQL job trace HTML summary to 16KiB

What does this MR do and why?

Prior to this change, individual lines in the GraphQL job trace HTML summary were unbounded in size. With this change, the total amount of bytes read from the raw trace is limited to 16 KiB.

This completes the rollout of the feature flag graphql_job_trace_html_summary_max_size.

Rollout issue: #425196 (closed)

Changelog: fixed

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