feat(@angular-devkit/architect): merge object options from CLI

[jkrems]

We recently introduced the ability to pass object values from the command line (#28362). @clydin noticed that the initial behavior didn't work well for --define: It completely replaced all values even if just one of multiple defines is specified.

This updates the architect to support merging of object options. If both the base option (e.g. from angular.json) and the override (e.g. from a CLI --flag) are objects, the objects are merged.

See: #28362

PR Checklist

Please check to confirm your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular-cli/blob/main/CONTRIBUTING.md#-commit-message-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

Issue Number: N/A

With multiple defines in angular.json, passing any define via the --define flag will ignore all existing defines.

What is the new behavior?

Only defines specified via the --define flag will be replaced. All others retain the value specified in angular.json.

Does this PR introduce a breaking change?

• Yes
• No

Other information

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