Remove multi-module workspace

[sevein]

Previously, we used a multi-module workspace (via the go.work file) to address issues with gopls detecting nested modules. However, these issues now appear to be resolved. Since the go.work file no longer provides any significant benefit, we're removing it from the project.

I've used go mod tidy -diff to check that the mod files are tidy. -diff is a new flag introduced in go1.23.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 55.45%. Comparing base (2cc4b26) to head (49319a8). Report is 4 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1045 +/- ## ========================================== - Coverage 55.52% 55.45% -0.07% ========================================== Files 103 103 Lines 6021 6021 ========================================== - Hits 3343 3339 -4 - Misses 2429 2432 +3 - Partials 249 250 +1 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.