crypto/ecdh: remove 8 byte pointer overhead for non-boringcrypto builds

[mateusz834]

This change makes the PublicKey and PrivateKey structs 8 bytes smaller,
by removing a pointer field from non-boringcrypto builds.

[gopherbot]

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[gopherbot]

Message from Gopher Robot:

Patch Set 1:

(1 comment)

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[gopherbot]

Message from Mateusz Poliwczak:

Patch Set 1: Commit-Queue+1

(1 comment)

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[gopherbot]

Message from Go LUCI:

Patch Set 1:

Dry run: CV is trying the patch.

Bot data: {"action":"start","triggered_at":"2024-09-21T19:13:13Z","revision":"bc06f2e52d210189425fc4f900379caddc71cacf"}

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[gopherbot]

Message from Mateusz Poliwczak:

Patch Set 1: -Commit-Queue

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[gopherbot]

Message from Go LUCI:

Patch Set 1:

This CL has passed the run

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Message from Go LUCI:

Patch Set 1: LUCI-TryBot-Result+1

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[gopherbot]

Message from Jorropo:

Patch Set 1: Code-Review+1

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