Add setting to toggle casing of SQL IntelliSense suggestions

[oseifrimpongg]

Currently, SQLTools always suggests SQL keywords in uppercase (e.g. SELECT, FROM, WHERE) during IntelliSense, regardless of the formatter configuration. For users who prefer writing SQL in lowercase, this may break consistency and slow down workflow.

While the extension supports formatting keywords to lowercase using:

"sqltools.format": {
  "reservedWordCase": "lower"
}

…the suggestions themselves still appear in uppercase while typing.

It would be helpful to have a setting to control the case of keyword suggestions as well — for example:

"sqltools.intellisense.keywordCase": "lower" // or "upper" (default)

This would help maintain visual consistency while writing and align IntelliSense behaviour with existing formatter preferences.

It’s a small change with a big impact on developer experience, thanks for the amazing work!