zipfile: Deduplicate reinitialization setup for ZipExtFile when seeking

Feature or enhancement

Proposal:

ZipExtFile needs to be reinitialized if seeking back beyond it's current buffered data. The code to initialize and then reinitialize are in 2 locations and consolidating these into one location reduces the footprint for introducing potential bugs.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-121640

从 ZipExtFile 开始检查 zipfile 的实现，并检查在 seeking 期间初始化或重新初始化它的两个位置。将这些设置路径合并到一个位置，然后验证向后 seeking 超出已缓冲数据时仍能正确重新初始化；相关 PR gh-121640 提供了上下文。