Fix accidental relative imports from non namespace barrels

[jakebailey]

Noticed in #59542; no file in our codebase should be bypassing the namespace barrels except those in src/compiler (in rare cases) or test code.

The only reason things didn't break is because these imports were done within services, which is only ever consumed by other entrypoints; if this had been done from say, tsserver, the magic import rewriting done in our build would have caused "double bundling" where we'd include the same code twice.

However, the fact that it did work implies that we could get away with direct imports except in our entrypoints, which is great because I thought I had unintentionally made direct imports impossible by making our package smaller. Turns out, no, we still can do it for anything without that magic build step.

[sheetalkamat]

Would prefer if this was some kind of warning if this is not desired. If we would do direct imports that would be ideal.

[jakebailey]

Yeah, I'll write a lint rule quick that prevents this; given it seems like we can actually do direct imports, but only in some project, we'd need that lint rule anyway, just applied to a different set of packages.