op-deployer: Separate L1 and L2 contract artifacts

[mslipper]

Adds support for specifying separate artifact URLs for L1 and L2. There are two new fields in the intent - L1ContractsLocator and L2ContractsLocator - which together replace the ContractArtifactsURL and ContractsRelease fields. Specifying a file or HTTPS URL for either field will automatically enable dev mode for the deployment. Specifying a tag:// URL will use the standard deployment for L1 and L2. The default have been set to the following:

• L1: op-contracts/v1.6.0
• L2: op-contracts/v1.7.0-beta.1+l2-contracts

Fixes https://github.com/ethereum-optimism/platforms-team/issues/337.

[semgrep-app]

Semgrep found 1 golang_fmt_errorf_no_params finding:

• op-supervisor/supervisor/backend/db/db_test.go
  • L280 - Triage

No fmt.Errorf invocations without fmt arguments allowed

_{Ignore this finding from golang_fmt_errorf_no_params.}

Semgrep found 1 math-random-used finding:

• op-supervisor/supervisor/backend/source/head_monitor_test.go
  • L7 - Triage

Do not use math/rand. Use crypto/rand instead.

_{Ignore this finding from math-random-used.}

Semgrep found 1 marshal-json-pointer-receiver finding:

• op-supervisor/supervisor/backend/db/heads/types.go
  • L99 - Triage

MarshalJSON with a pointer receiver has surprising results: golang/go#22967

_{Ignore this finding from marshal-json-pointer-receiver.}

Semgrep found 1 err-nil-check finding:

• op-supervisor/supervisor/backend/db/db.go
  • L108-112 - Triage

superfluous nil err check before return

_{Ignore this finding from err-nil-check.}

[blmalone]

lgtm.

One small, non-blocking question.

Side note:
AFAIK, op-chain-ops/deployer/integration_test/apply_test.go only tests the flow were ArtifactsLocator has a URL and not a Tag. Given that the most common production execution of the apply command will be with the Tag field set, I think an additional test for this would be useful. I made an issue for this here.