feat(@schematics/angular): add migrate-karma-to-vitest update migration

[clydin]

Migrate projects using the Karma unit-test builder to the new @angular/build:unit-test builder with Vitest.

This migration automatically updates target builders, translates builder options (such as coverage and browsers format), moves custom build options to dedicated configurations to prevent loss of custom settings, cleans up default configuration files, and installs required Vitest runner packages.

[gemini-code-assist]

Code Review

This pull request introduces a new schematic to migrate Angular projects from the legacy Karma unit-test builder to the new Vitest-based unit-test builder. The changes include logic to map Karma configurations, coverage settings, and build options to the new builder, along with necessary dependency updates. Feedback was provided regarding potential configuration overwrites when processing build options, the risk of duplicate entries in the setupFiles array, and the recommendation to use node:util's isDeepStrictEqual instead of JSON.stringify for robust object comparison.

[alan-agius4]

LGTM. Just a NIT

[clydin]

This PR was merged into the repository. The changes were merged into the following branches:

• main: be60a63

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