feat: support for external libs (DO NOT MERGE)

.github/workflows/mirror-external_libs.yml

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+# We push using git subrepo (https://github.com/ingydotnet/git-subrepo)
+# with some logic to recover from squashed parent commits
+# We first identify ourselves, needed to commit.
+# Then push to subrepo, commit to master. The commit is needed
+# to continue to replay. If we still hit issues such as this
+# action failing due to upstream changes, a manual resolution
+# PR with ./scripts/git_subrepo.sh pull will be needed.
+name: Mirror Repositories
+on:
+  schedule:
+    # Run the workflow every night at 2:00 AM UTC.
+    - cron: "0 2 * * *"
+  workflow_dispatch: {} 
+
+jobs:
+  mirror-to-noir-edwards-lib:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Push to external libs repo
+        run: |
+          SUBREPO_PATH=external_libs/noir-edwards
+          git config --global user.name AztecBot
+          git config --global user.email [email protected]
+
+          if ./scripts/git_subrepo.sh push $SUBREPO_PATH --branch=master; then
+            git fetch # in case a commit came after this
+            git rebase origin/master
+            git commit --amend -m "$(git log -1 --pretty=%B) [skip ci]"
+            git push
+          fi
+
+

external_libs/noir-edwards/.gitignore

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+target

external_libs/noir-edwards/.gitrepo

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+; DO NOT EDIT (unless you know what you are doing)
+;
+; This subdirectory is a git "subrepo", and this file is maintained by the
+; git-subrepo command. See https://github.com/ingydotnet/git-subrepo#readme
+;
+[subrepo]
+	remote = https://github.com/zac-williamson/noir-edwards.git
+	branch = main
+	commit = 0016ce82cd58b6ebb0c43c271725590bcff4e755
+	parent = e1bcb73f8c2e2c6786faeb18b8ce070a2400635d
+	method = merge
+	cmdver = 0.4.6

external_libs/noir-edwards/Nargo.toml

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+[package]
+name = "edwards"
+type = "lib"
+authors = [""]
+compiler_version = ">=0.30.0"
+
+[dependencies]

external_libs/noir-edwards/README.md

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+# noir-edwards
+
+Optimized implementation of Twisted Edwards curves.
+
+Uses lookup tables and maximally efficient representations of group operations (for width-4 noir) to efficiently implement scalar multiplication and multiscalar multiplication.
+
+Cost of 1 scalar mul = 2232 gates. Marginal cost of additional muls in an msm = 972 gates.
+
+For example usage see `test.nr`
+
+List of potential optimizations to improve performance:
+
+1. update barretenberg backend to identify when memory lookups always come in pairs. e.g. two MEM operations, different ids, read index is the same. backend can convert into 1 memory table with 2 values instead of 2 memory tables with 1 value
+
+```
+MEM (id: 1, read at: x1, value: x125)
+MEM (id: 2, read at: x1, value: x126)
+```
+
+2. fix barretenberg bug where range checks for values <2^{14} create an unneccessary addition gate.

external_libs/noir-edwards/info.sh

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+nargo compile --force && bb gates -b ./target/edwards.json

external_libs/noir-edwards/src/bjj.nr

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+use crate::TECurveParameterTrait;
+use crate::Curve;
+
+struct BabyJubJubParams {}
+impl TECurveParameterTrait for BabyJubJubParams {
+    fn a() -> Field { 168700 }
+    fn d() -> Field { 168696 }
+    fn gen() -> (Field, Field) { (0x0bb77a6ad63e739b4eacb2e09d6277c12ab8d8010534e0b62893f3f6bb957051, 0x25797203f7a0b24925572e1cd16bf9edfce0051fb9e133774b3c257a872d7d8b)}
+}
+type BabyJubJub = Curve<BabyJubJubParams>;