Add explicit parameter variants to ec_*_pub data files

[Marandil]

Description

Add explicit parameter variants to ec_*_pub data files. These are required for the new tests included in
Mbed-TLS/TF-PSA-Crypto#705 and Mbed-TLS/mbedtls#10630

The variants have been generated with the following command:

openssl ec -pubin -param_enc explicit -pubout -in ec_XYZ_pub.der -out ec_XYZ_pub.expl.der -outform der

(with the proper choice of XYZ or der/pem)

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 PR provided Fix explicit Elliptic Curve parsing TF-PSA-Crypto#705
• development PR not required because: no changes to development
• 3.6 PR provided Fix explicit Elliptic Curve parsing (3.6 backport) mbedtls#10630

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[gilles-peskine-arm]

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