feat: Added historical migration option

[benjackwhite]

Problem

We have an optimisation flag for historical migrated data documented here but we don't expose a way of configuring it.

Changes

• Adds the option

Release info Sub-libraries affected

Bump level

• Major
• Minor
• Patch

Libraries affected

• All of them
• posthog-web
• posthog-node
• posthog-react-native

[github-actions]

Size Change: +168 B (+0.23%)

Total Size: 73.5 kB

Filename	Size	Change
posthog-node/lib/index.cjs.js	20 kB	+42 B (+0.21%)
posthog-node/lib/index.esm.js	20 kB	+42 B (+0.21%)
posthog-web/lib/index.cjs.js	16.8 kB	+42 B (+0.25%)
posthog-web/lib/index.esm.js	16.7 kB	+42 B (+0.25%)

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