Update @kusto/language-service-next

[rosshamish]

Update @kusto/language-service-next to the 11.5.* line, which was published 3 months ago and is getting regular updates. This dependency was previously pinned to an old pre-release version (0.0.28-rc.1) which was used during the original hackathon back in 2019 that this extension was created during.

Fixes bug #5
Also fixes bug #126 in passing.

Additional changes:

• some updates to deal with some breaking changes made to types - nothing too scary, mostly types getting upgraded to be nullable, or constructors changing order and therefore changing names
• remove hand-written type definitions that were needed to get the typescript build passing (e.g. kusto-language-server/server/out/Kusto.Language.Bridge.min.js)
• remove peer dependencies that were needed to patch things up back then (the legacy language service package, the monaco package). These are no longer needed anymore - everything is included in the latest language service package.
• update the typescript version in use to 5.* - this is parity with the Azure/monaco-kusto package, which is a more well-supported sibling of this one and is worth referring to.
• update the node version used in CI to 20 (was: 12)
• update @types/node, needed for CI to pass during npm run vscode:prepublish, see https://stackoverflow.com/questions/57331779/typescript-duplicate-identifier-iteratorresult

Testing:

• Launches without crashing
• Format document: seems to be working, and bug Formatting Issue: Unintended Syntax Changes in Code Prettification #126 no longer repros
• Autocomplete: seems to be working
• Hover info: seems to be working