rename ConfigurationRawJSON -> Configuration

[slimsag]

In the near future this will return a data structure and the name suffix
RawJSON no longer makes sense in that context. I am reducing the size of my
other PR's diff, and as such merging this separately.

[codecov-io]

Codecov Report

Merging #1168 into master will decrease coverage by 0.25%.
The diff coverage is 0%.

Impacted Files	Coverage Δ
pkg/conf/client.go	14.81% <0%> (+0.26%)	⬆️
cmd/frontend/internal/httpapi/internal.go	0% <0%> (ø)	⬆️
cmd/frontend/internal/httpapi/httpapi.go	19.1% <0%> (ø)	⬆️
cmd/frontend/auth/providers.go	0% <0%> (-25.81%)	⬇️
cmd/frontend/internal/authz/register.go	0% <0%> (-14.29%)	⬇️
cmd/frontend/registry/backcompat.go	13.04% <0%> (-4.67%)	⬇️
pkg/gosrc/import_path.go	87.75% <0%> (-1.64%)	⬇️
pkg/diskcache/cache.go	42.6% <0%> (-0.99%)	⬇️
enterprise/cmd/xlang-go/internal/server/deps.go	80.85% <0%> (-0.86%)	⬇️
enterprise/cmd/frontend/auth/githuboauth/config.go	33.33% <0%> (-0.6%)	⬇️
... and 13 more

[slimsag]

Helps #965