chore: introduce support for NPM_DEPLOY config for MFEs wrt uploading JS source maps to Datadog

[adamstankiewicz]

The datadog-ci command, installed via the @datadog/datadog-ci NPM package appears to be missing in the current implementation of the FrontendDeployer on a recent test of the stage deployment pipeline:

/bin/sh: 1: ./node_modules/.bin/datadog-ci: not found
b'Deploy frontend: Uploading source maps to Datadog for app frontend-app-learner-portal-enterprise.'
b'Deploy frontend: Could not upload source maps to Datadog for app frontend-app-learner-portal-enterprise.'

This issue is likely due to the @datadog/datadog-ci NPM package only getting installed during FrontendBuilder, such that when FrontendDeployer is run, the previously installed NPM package exposing the datadog-ci command is no longer installed since it's a separate environment from the FrontendBuilder.

Given this issue, this PR proposes setting a NPM_DEPLOY config setting in edx-internal's common MFE configuration, defining NPM packages to be installed for the purpose of deployment. For now, this would only be @datadog/datadog-ci, but could be expanded for future use cases as well.

The alternative considered was having FrontendBuilder install the @datadog/datadog-ci NPM package directly (hardcoded in edx/tubular). However, this approach was decided against in favor of the more generalized NPM_DEPLOY defined via edx-internal's common MFE configuration instead, for parity with NPM_PRIVATE and NPM_ALIASES.

NPM_PRIVATE are private packages that the build application relies on; similarly, NPM_ALIASES are installed packages that are aliased via package.json definitions.

NPM_DEPLOY differs because the packages listed here are not relevant to the built application; only in support of the deployment.

Related PRs:

• https://github.com/edx/edx-internal/pull/11050