Validate EC_PUB_X/EC_PUB_Y on import by routine them through the X9.63 point import

[gasbytes]

Route EC_PUB_x/EC_PUB_Y through wc_ecc_import_x963_ex, the same validated import the encoded public key path uses, so the point is checked to be onn the curve,
both ordinates are required together, and the projective z ordinate is set.

Also, added some 3 regression tests for the off-curve and X-without-Y cases to test the edge cases of this behaviour.

Fixes F-4694.

[Copilot]

Pull request overview

This PR hardens ECC public key imports by validating raw EC_PUB_X/EC_PUB_Y coordinates via the same X9.63 point import path already used for encoded public keys, ensuring points are on-curve and that X/Y are provided together. It also adds regression tests to cover off-curve and incomplete-coordinate edge cases.

Changes:

• Route EC_PUB_X/EC_PUB_Y imports through wc_ecc_import_x963_ex() by constructing an uncompressed X9.63 point, enforcing on-curve validation and proper point initialization.
• Reject public key imports that provide only one ordinate (X without Y, or vice versa).
• Add regression tests for off-curve XY import rejection, X-only rejection, and an ECDH derive check with an off-curve peer key.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
test/test_ecc.c	Adds regression tests for off-curve and incomplete-coordinate public key imports, plus an ECDH-path guard test.
src/wp_ecc_kmgmt.c	Validates EC_PUB_X/EC_PUB_Y imports by converting to an X9.63 point and importing via wc_ecc_import_x963_ex().

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