Remove solution style tsconfig

[cseas]

Use Case

The solution style tsconfig was added to the project as part of an upgrade to Angular 10 but this change was rolled back soon after in the next patch release.

The project is now on Angular 12 but still has the solution style tsconfig. This file should've been removed as part of Angular 10 minor update.

Keeping this file around is going to cause issues upgrading packages since Angular packages throw an error if tsconfig.base.json is present in the project. Example

Proposal

Remove the solution style tsconfig. Simply deleting the file will throw typescript errors in VSCode in random file (e.g. explorer.component.test.ts) so replacement config needs to be setup where required.

[cseas]

@aaron-steinfeld @anandtiwary @itssharmasandeep