feat(schema): show dictionary encoding in column schemas

[lberserq]

Columnar table schemas currently show compression without indicating dictionary encoding. Add an Encoding column to the schema sidebar and Diagnostics → Schema, with a Dictionary label for enabled columns and sorting that brings them first.

Recognize both DataAccessorConstructor.ClassName = "DICTIONARY" and legacy DictionaryEncoding.Enabled, giving the current accessor precedence. Missing, disabled, and unknown settings remain unmarked. The label reflects the configured schema encoding.

Validation on the PR branch:

• npm run typecheck, npm run lint (existing warnings only), npm test -- --runInBand (237 suites / 2,182 tests), npm run build:embedded, and npm run package passed.
• Regression tests cover both response formats, conflicting settings, missing/unknown values, compression display, and row-table behavior.
• Chromium rendering and sorting checked against the PR production build with controlled viewer responses. No local backend was available; WebKit was blocked by missing host libraries.

Screenshot with demo schema data:

Full-size screenshot (Yandex internal)