feat: Add BLS signature short pk variant

[alxiong]

Description

Major changes include:

• move current bls_over_bn254 impl to bls_over_bn254::min_sig
• add bls_over_bn254::min_pk module

closes: #373

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Before we can merge this PR, please make sure that all the following items have been
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• Targeted PR against correct branch (main)
• Linked to GitHub issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• Wrote unit tests
• Updated relevant documentation in the code
• Added a relevant changelog entry to the Pending section in CHANGELOG.md
• Re-reviewed Files changed in the GitHub PR explorer

[mrain]

Is this still working? We may still want a short pk version for a smaller stake table.
cc @alxiong

[alxiong]

I see! I paused this previously, but I will keep working on it this week. Thanks for reminding me! @mrain

[chancharles92]

I see! I paused this previously, but I will keep working on it this week. Thanks for reminding me! @mrain

Thanks @alxiong ! Let me know when it's ready.