Remove backtracking from parsing tarfile members and headers

[sethmlarson]

Bug description:

Today the tarfile module parsing of header values allows for backtracking when parsing header values. Headers have a well-known format that doesn't require backtracking to parse reliably, the new method of parsing will only require a single pass over a byte stream.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-121285: Remove backtracking when parsing tarfile headers #121286
• [3.13] gh-121285: Remove backtracking when parsing tarfile headers (GH-121286) #123542
• [3.12] gh-121285: Remove backtracking when parsing tarfile headers (GH-121286) #123543
• [3.11] gh-121285: Remove backtracking when parsing tarfile headers (GH-121286) #123639
• [3.10] gh-121285: Remove backtracking when parsing tarfile headers (GH-121286) #123640
• [3.9] gh-121285: Remove backtracking when parsing tarfile headers (GH-121286) #123641
• [3.8] gh-121285: Remove backtracking when parsing tarfile headers (GH-121286) #123642

[gpshead]

main version merged. I'll let you work out any non-automatic backports.