Skip experimental packets (tags 60-63) in permissive key import mode

[kaie]

Fixes: #2379

[kaie]

FYI, the test key was created using the following approach:

Used existing test key (dsa-eg-pub.asc), decoded it from ASCII armor to binary, then appended a manually constructed experimental packet:

• Tag byte: 0xFC = 0xC0 | 60 — new-format packet header with tag 60
• Length byte: 0x04 — 4 bytes of content follow
• Content: 0xDE 0xAD 0xBE 0xEF — arbitrary placeholder bytes

Then re-armored the result (base64 + CRC24 checksum) back into a .asc file.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.46%. Comparing base (83a987a) to head (cc8d63e).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2385   +/-   ##
=======================================
  Coverage   85.46%   85.46%           
=======================================
  Files         126      126           
  Lines       22711    22716    +5     
=======================================
+ Hits        19409    19414    +5     
  Misses       3302     3302           

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