Remove Keystone from existing tests (trailofbits#1684)

* Cache generated ASM

* Never install Keystone on the CI

* Fix dict retreival one-liner

arguments aren't lazily evaluted, so ks_assemble always got called

* Apply suggestions from code review

Docstrings and type hints

Co-authored-by: Brad Larsen <brad.larsen@trailofbits.com>

* Update tests/native/test_armv7cpu.py

Missed one

Co-authored-by: Brad Larsen <brad.larsen@trailofbits.com>

Co-authored-by: Brad Larsen <brad.larsen@trailofbits.com>

.github/workflows/ci.yml

@@ -52,11 +52,7 @@ jobs:
         # Install solc unconditionally because it only takes a second or two
         sudo wget -O /usr/bin/solc https://github.com/ethereum/solidity/releases/download/v0.4.24/solc-static-linux
         sudo chmod +x /usr/bin/solc
-        EXTRAS="dev-noks"
-        if [[ "$TEST_TYPE" == "native" ]]; then
-          EXTRAS="dev"
-        fi
-        pip install -e .[$EXTRAS]
+        pip install -e ".[dev-noks]"
     - name: Run Tests
       env:
         TEST_TYPE: ${{ matrix.type }}