[FLINK-39191][runtime-web] Upgrade monaco-editor to 0.55.1

[gkomlossi]

What is the purpose of the change

Upgrade the monaco-editor to version 0.55.1 to avoid CVEs caused by DOMPurify, which monaco-editor depends on.

Brief change log

• the monaco-editor version is updated in package.json and package-lock.json has been regenerated.
• minor code change is required in task-manager-thread-dump.component.ts due to the new version of the editor API.

Verifying this change

Tested locally.

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

[flinkbot]

CI report:

• 6ea8216 Azure: FAILURE

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[featzhang]

Could you add a short note in the PR description about the motivation for upgrading monaco-editor?
For example: security fixes, compatibility, or feature updates.

Have we verified the Web Dashboard thread-dump page manually after the upgrade?
Since this is a major version jump for Monaco, a quick UI check would be helpful.