[FLINK-37151][runtime-web] Remove redundant testing dependencies and files

[Laffery]

JIRA Ticket: issues.apache.org/jira/browse/FLINK-37151

What is the purpose of the change

Remove redundant testing dependencies and testing files, because they are useless.

Brief change log

• remove testing deps such as @testing-library/angular karma jasmine protractor
• remove testing files *.spec.ts
• remove other useless files and configuration

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[Laffery]

This PR had been reviewed by @davidradl in #25997

[flinkbot]

CI report:

• 61c2cd6 Azure: SUCCESS

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[Sxnan]

Thanks for the PR! LGTM.