Stored (uncompressed) ZipExtFile in zipfile can be seekable at lower cost

[JuniorJPDJ]

BPO	44173
Nosy	@Yhg1s, @gpshead, @serhiy-storchaka, @JuniorJPDJ
PRs	bpo-44173: better approach for seeking in non-compressed ZipExtFile #26227 gh-88339: enable fast seeking of uncompressed unencrypted zipfile.ZipExtFile #27737

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/gpshead'
closed_at = None
created_at = <Date 2021-05-19.02:28:39.857>
labels = ['type-feature', 'library', '3.11']
title = 'Stored (uncompressed) ZipExtFile in zipfile can be seekable at lower cost'
updated_at = <Date 2021-08-18.17:30:30.110>
user = 'https://github.com/JuniorJPDJ'

bugs.python.org fields:

activity = <Date 2021-08-18.17:30:30.110>
actor = 'gregory.p.smith'
assignee = 'gregory.p.smith'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-05-19.02:28:39.857>
creator = 'juniorjpdj'
dependencies = []
files = []
hgrepos = []
issue_num = 44173
keywords = ['patch']
message_count = 1.0
messages = ['393918']
nosy_count = 5.0
nosy_names = ['twouters', 'gregory.p.smith', 'alanmcintyre', 'serhiy.storchaka', 'juniorjpdj']
pr_nums = ['26227', '27737']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue44173'
versions = ['Python 3.11']

[JuniorJPDJ]

At the moment stored ZipExtFile is being read to the place of seek like all other compressed variants.
It's not needed as it's possible to freely seek uncompressed file inside zip without this penalty.

Lots of apps depend on ZipExtFile seeking ability and it would lower performance and IO penalty significantly.

I've POC patch created.
It disables CRC checking after first seek as it's impossible to check CRC if we are not reading whole file.