Update kusto-language-server validation & publish workflows

[rosshamish]

Validation workflow:

• run on path "kusto-language-server/**"
• npm ci
• npm run vscode:prepublish

Publish workflow:

• run on path "kusto-language-server/**"
• fixup

package.json:

• update dependencies, npm audit fix, migrate off ancient vscode dev dependency

[rosshamish]

(Changelog Bot) Thanks for the patch! Please be sure to update CHANGELOG.md with a short summary of the changes in this pull request.