Add the available labels when a kind dependency cannot be found

[gregtatum]

This makes it easier to debug errors in your Taskgraph generation.

Exception: distillation-student-model-quantize-en-ru can't fetch inference-build artifacts because there are no tasks with label inference-build in kind dependencies!
Available tasks:
 - toolchain-cuda-toolkit
 - toolchain-cuda-toolkit-11
 - toolchain-marian
 - toolchain-marian-cpu
 - toolchain-fast-align
 - toolchain-preprocess
 - toolchain-extract-lex
 - toolchain-kenlm
 - toolchain-cyhunspell
 - corpus-merge-devset-en-ru
 - build-vocab-en-ru
 - inference-test
 - inference-build-wasm
 - inference-test-wasm
 - distillation-corpus-build-shortlist-en-ru
 - distillation-student-model-finetune-en-ru

[bhearsum]

Thank you!