fix: replace deprecated and internal IntelliJ APIs

[mdelambilly]

Summary

• Replace ComponentManager.getComponent(EditorFactory) with EditorFactory.getInstance()
• Replace Guava Charsets.UTF_8 with StandardCharsets.UTF_8
• Migrate JsonParser.Feature to JsonReadFeature (Jackson 2.12+)
• Replace BalloonPopupBuilderImpl with JBPopupFactory.createBalloonBuilder()
• Remove ReadAction wrapper in FileUtil — fixes crash when opening a datasource whose scratch file does not exist yet
• Replace deprecated ActionUtil.invokeAction with direct actionPerformed call in CypherLineMarkerProvider
• Replace deprecated PluginDescriptor.isEnabled() with null check

Test plan

• Plugin loads without error
• Double-click on datasource opens the Cypher file without crash
• Gutter play button executes the query
• JSON parameters with non-strict syntax (single quotes, comments) parse correctly

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