Pass common CI vars into builder as build args

[ipmb]

Convert these Codebuild specific vars into more standard names and pass in as build args to the docker image

Purpose	CodeBuild Var	Neutral / “Industry-standard” Name	Why
Source ref (branch or tag)	CODEBUILD_WEBHOOK_HEAD_REF	CI_COMMIT_REF	GitLab CI, Drone, Buildkite use this. GitHub Actions has GITHUB_REF which is similar.
Commit SHA	CODEBUILD_RESOLVED_SOURCE_VERSION	CI_COMMIT_SHA	Widely adopted (CI_COMMIT_SHA in GitLab, GITHUB_SHA in Actions, DRONE_COMMIT_SHA, etc.).
Build start time	CODEBUILD_START_TIME	CI_BUILD_STARTED_AT	Less standardized, but GitLab/Drone use CI_PIPELINE_CREATED_AT or DRONE_BUILD_STARTED. The CI_BUILD_* prefix keeps it consistent.
Repository URL	CODEBUILD_SOURCE_REPO_URL	CI_REPOSITORY_URL	Common in GitLab and others (CI_REPOSITORY_URL gives the clone URL).

Note that CODEBUILD_WEBHOOK_HEAD_REF is only set on builds triggered by a webhook. For a manual build, we should use the the branch it pulled from. It may make more sense to use CODEBUILD_SOURCE_VERSION.

Docs: https://docs.aws.amazon.com/codebuild/latest/userguide/build-env-ref-env-vars.html