Stop uploading environmentVariables in apify push #1575

apify push sends environmentVariables from actor.json in the version update, which replaces the whole env var list on the platform. Variables set only in Apify Console are deleted. After this change, apify push deploys code only, and CLI-pushed and Git-sourced Actors behave the same.

Scope

• Never send envVars from apify push (src/commands/actors/push.ts).
• When actor.json has a non-empty environmentVariables, print a warning: the values apply to local runs only, and apify env push or Console sets them on the platform.
• Turn --allow-missing-secrets on push into a no-op and mark it as deprecated.
• Keep sending applyEnvVarsToBuild (the flag and the actor.json field). It's a build setting, not a value.
• Add a section to MIGRATIONS.md and to the release notes. This is a breaking change for creators who set platform env vars only through push.

Rollout

Ship in the same release as apify env push, so those creators have a replacement from day one.

Done when

• A push with environmentVariables leaves the platform env vars untouched. An API test covers it.
• The warning is shown, and the telemetry counts are still recorded.

Depends on

• apify env push (Add apify env push #1572)
• Push telemetry for the baseline (Record environmentVariables usage in apify push telemetry #1567)