Enable configuring template type checking separately from their TS file components

[runspired]

Building on #269 (ensure no type-checking for files that have JS component files), in a large migration it is often beneficial to have two tiers of migration: files that have been migrated fully to strict-mode and files that may still tolerate some usage of implicit any. This can be enforced nicely by using two tsconfigs, one for strict files and a second that loosens the rules slightly for non-strict files. An example of this sort of configuration for a migration can be found here

Allowing these two tiers enables applications to make better use of tooling and quick-wins for programmatically converting part-way to typescript where possible so as to start receiving benefits sooner while working through the longer-tail conversion to strict mode.

Currently glint couples the type checking to the associated TS file; however, since it represents a distinct program and since templates are far more prone to importing functions from throughout the application that may not have been typed yet, this prevents using glint at all when TS files have been typed strictly but the associated template files still rely on implicit-any. Rather than forcing these users to make their tsconfig less-strict so as to be able to adopt glint even partially, we should allow them to treat template files in a looser way if so needed.