This reverts commit 87ae3a38.

For #74846

Migrates from using the heap service to have an explicit lifecycle

Part of #74846

Code Actions can use commands internally, which must be disposed of. We were previously using the heap service for this but this will not work for the web. Add a custom lifecycle instead

debt - decouple webviews from code insets, move things to /browser/-layer, change inset api proposal to push style, re #66418

add uri-property to CallHierarchtItem, better wording, better behaviour when switching calls/callers

- annotate undefined returned types
- Don't call functions with null or undefined values.
- Refactor _convertCompletionItem so that we don't need to mutate the returned object
- Suppress a type error related to electricCharacters.

Const provides better type guards and can make logic clearer