internal/lsp: implement organise imports code action
For now, this is limited to sorting blocks of imports, and removing
unused imports.
Signed-off-by: Matthew Sackman <matthew@cue.works>
Change-Id: I8810191c56bdb4df00b5e674ac364051bc689b5a
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1235340
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>