Add X.509 fuzzing seeds

[JulioLoayzaM]

Description

Adds six new fuzzing seeds for X.509, targeting cases that are not covered by the current corpus. Includes additions to the data_files/Makefile to re-generate some of the seeds, and a Python script to generate those that are easier to build manually rather than using openssl.

PR checklist

Please add the numbers (or links) of the associated pull requests for consuming branches. You can omit branches where this pull request is not needed.

• TF-PSA-Crypto development PR not required because: this only affects fuzzing.
• TF-PSA-Crypto 1.1 PR not required because: this only affects fuzzing.
• mbedtls development PR not required because: this only affects fuzzing.
• mbedtls 4.1 PR not required because: this only affects fuzzing.
• mbedtls 3.6 PR not required because: this only affects fuzzing.

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