Scoring: test against local scip-ctags (#677)

This change refactors our end-to-end scoring tests and enables local testing
using the scip-ctags binary:
* Split scoring tests out of `e2e_test` and into their own file `scoring_test`
* Split huge test methods into targeted ones like `TestFileNameMatch`,
`TestJava`, `TestGo`, etc.
* For languages that scip-ctags supports, rerun the same cases using the
scip-ctags binary

To run scip-ctags tests locally, you can set the env variable
```
SCIP_CTAGS_COMMAND=<sourcegraph-repo>/dev/scip-ctags-dev
```

This doesn't yet update Zoekt CI to run scip-ctags tests. That will be tackled
in a follow-up.