[context-zone] drop support for old zone.js versions

[pichlermarc]

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Description

While reviewing the packages @opentelemetry/context-zone and @opentelemetry/context-zone-peer-dep for any changes that we can do in 2.0 to reduce required maintenance effort, I found that we could likely drop support for old versions and only support the currently latest minor version (currently 0.15). Another option may be to support only the minor versions that had releases in the last year (0.15.x, 0.14.x)

We don't depend on any SDK packages so if users need support for old versions they could still use it by not upgrading to 2.0.

Submitting this issue to collect feedback on the topic.

cc @open-telemetry/javascript-maintainers

Additional context

• currently supported versions: https://github.com/open-telemetry/opentelemetry-js/blob/fddcd199a08d74a058d1c2d601f4e62966f208c0/packages/opentelemetry-context-zone-peer-dep/package.json#L85