Migrate remaining JS/JSX files to TypeScript and improve type safety

[dennisoelkers]

Description

Motivation and Context

• Migrate ~90 remaining .js/.jsx files to TypeScript (.ts/.tsx), bringing the codebase to near-complete TypeScript coverage
• Eliminate all as any casts introduced during migration, and reduce remaining as casts to only those structurally necessary
  (Immutable.js .toJS(), Reflux createActions, plugin binding contravariance, union narrowing)
• Add proper types to stores and utilities that previously returned any: Store.get<T>(), Store.sessionGet<T>(),
  getValueFromInput(), SystemJobsActions.list(), and typed fetch<T>() generics across multiple Reflux stores

Details

Migrated files span actions, stores, logic/utility modules, components, tests, and barrel/index files. A small set of .js files are intentionally kept: ACE editor mode files, webpack-entry.js, polyfill.js, and logic/index.js (webpack require.context).

Type safety improvements:

• Store.get / Store.sessionGet are now generic (get<T>(key): T | undefined) instead of returning any
• getValueFromInput returns string | number | boolean | undefined instead of any
• SidecarStatusEnum properties and methods are fully typed
• Reflux store actions use fetch<T>() generics to type API responses (EventDefinitionsStore, SimulatorStore, SystemJobsStore,
  EnterpriseStore, EventsStore, PluginsStore)
• Event handlers narrowed from SyntheticEvent to React.ChangeEvent<HTMLInputElement> where applicable

/nocl No user-facing change.
/prd Graylog2/graylog-plugin-enterprise#13306

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have requested a documentation update.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[linuspahl]

These changes look good to me!

[linuspahl]

As far as I can tell we don't need to use as string here and in similar cases.

[dennisoelkers]

✅

[linuspahl]

I noticed that we sometimes use as to cast the result of getValueFromInput and sometimes we use String() or Boolean(). Is there a reason for it?

[dennisoelkers]

The first was Claude's attempt to do it, I corrected it to use String/Boolean, but it seems like it did not track back all of its changes :/

[dennisoelkers]

Fixed these and other occurences.