chore: simpler ber2der with length check

[ibukanov]

Do not build an intermediate tree presentation of BER format in ber2der. Rather write the data directly to the output array patching the length header as necessary.

Protect against int32 overflow on 32-bit CPU when calculating the BER content length.

Detect and report invalid BER when a fixed length of the sequence does not match the actual length of children.

Name of feature:

Stricter definite length handling in BER data.

Pain or issue this feature alleviates:

Invalid BER data generator can be detected.

Why is this important to the project (if not answered above):

Is there documentation on how to use this feature? If so, where?

In what environments or workflows is this feature supported?

In what environments or workflows is this feature explicitly NOT supported (if any)?

Supporting links/other PRs/issues:

💔Thank you!

[hslatman]

Hey @ibukanov, thank you for working on this. This looks like a great improvement! I need some time to grok it all for proper review 😅

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