build: upgrade TypeScript to 7.0 - #56

From Node v6, you have to explicitly include type modules, otherwise they will not be added globally to the project like `process` for Node, and module imports will error like `Cannot find name 'node:fs'`.

- Added `types` array to tsconfig and included the `node` and `vscode` modules to fix import and usage errors.

Ref: http://typescriptlang.org/tsconfig/#types

Fixed TS 7.0 errors by ensuring:

- Variables don't have `undefined` or `null` values before accessing them and providing fallback values if they are undefined with the null coalescing operator (??) and conditional ternary operator (? .. : .. ).

- Values from methods are satisfying their expected return types using the `as` keyword and generic typed method calls.

- Object keys aren't accessed if the object itself is `undefined` with the optional chaining operator (?.) and proper undefined type guards and conditionals.

- `reconstructRegex` util function infers the correct type from the passed `obj` param.

- Error stack logging has a fallback of the error message in case the stack is null/undefined.

- `convertMapToReversedObject` util function has properly typed `result` instead of implicit `any` type and changed the reverse object mapping to mutate the existing array instead of rebuilding a new one on every iteration.

- Changed type of `packageJsonData` property to allow it to be `null`.

- Moved the null check from the `constructor` to the `setExtensionData` method, and use the check to narrow the type and assert that it's not null/falsy, and return early if it is. Using a local variable instead of accessing the property directly ensures TS doesn't keep spitting out null possibility errors.

- Removed the now redundant `setupOutputChannel` Logger method and it's references, this is because the output channel is now setup in the `constructor` so we have no need for this method now.

- Removed the redundant `outputChannel` property null check in `showChannel` method since it's never null as it's initialised in `constructor`.

If an error code was caught but isn't listed in the messages map, then the `errorMsg` in `validateDevEnvVariables` utils function would return something like "ENOTDIR: undefined: ...".

- Fixed by adding a fallback to the `UKNOWN` entry when an error code is not mapped.