Address plugin verifier warnings

[r-ralph]

Fix some warnings reported by plugin verifier.

1. Stop using deprecated functions in HtmlSyntaxInfoUtil.
   a. Some of these APIs will apparently be removed in the most recent release (2024.3)
2. Supporting K2 mode
   a. Follow the migration guide and change to use the Analysis API used in K2 mode.
   b. https://kotlin.github.io/analysis-api/migrating-from-k1.html
   c. Also, Kotlin plugin was changed to a required plugin because K2 mode specification and optional could not be described at the same time.
3. Indicate that this plugin can be applied without requiring a restart of the IDE.

In addition, the following issues found during these corrections will be corrected:

1. Fix to correctly display icons even when only field is written such as static import.

[munetoshi]

LGTM!