Improve security by updating blst to version 0.3.12

[vtamara]

Context and scope
Currently subnet-evm uses the version 0.3.11 of the library blst to implement the cryptographic signature BLS12-381. The version 0.3.12 of blst improves security as described in its release notes https://github.com/supranational/blst/releases/tag/v0.3.12 and in particular includes the commits supranational/blst@dae1f94 and supranational/blst@6cca12a that

1. Improve security of the library by moving constants to a read-only section (not allowing attackers to modify the constants after the program starts)
2. Works with OpenBSD/adJ and advances #2782. Due to security policies of that OS the previous version 0.3.11 with avalanchego produced segmentation faults sporadically, see Segmentation fault in some machines and not in others using OpenBSD adJ74 supranational/blst#206 The issue was solved with the mentioned commits included in version 0.3.12.

Discussion and alternatives
IMHO it is a good security practice to update version of libraries periodically.

Open questions
See ava-labs/avalanchego#3079 , ava-labs/coreth#614 and ava-labs/avalanche-network-runner#724