The dockerfile was failing on the step due to `python` no longer
existing in the alpinelinux archives. This commit updates the
version of `python` to `python3` so that the deployer image
can build properly. Also update the integration-tests image
to use python3 and the deployer entrypoint script to use python3

```
 > [ethereumoptimism/deployer:latest stage-1  2/13] RUN apk add --no-cache git curl python bash jq:
124 2.190 fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/main/x86_64/APKINDEX.tar.gz
124 2.170 fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/main/x86_64/APKINDEX.tar.gz
124 2.803 fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/community/x86_64/APKINDEX.tar.gz
124 2.783 fetch https://dl-cdn.alpinelinux.org/alpine/v3.14/community/x86_64/APKINDEX.tar.gz
124 6.396 ERROR: unable to select packages:
124 6.416 ERROR: unable to select packages:
124 6.431   python (no such package):
124 6.431     required by: world[python]
124 6.451   python (no such package):
124 6.451     required by: world[python]
```