Consider renaming SPAN_STORAGE env var to SPAN_STORAGE_TYPE

[yurishkuro]

I noticed this discussion about Jaeger Helm chart: helm/charts#3109 (comment)

The original --span-storage.type cli switch that was deprecated in #625 in favor of SPAN_STORAGE env var was actually previously mapped to SPAN_STORAGE_TYPE env var.

We could achieve better backwards compatibility by renaming

• SPAN_STORAGE => SPAN_STORAGE_TYPE
• DEPENDENCY_STORAGE => DEPENDENCY_STORAGE_TYPE (for consistency).

Worth it? It does take more characters to type.

cc @black-adder @objectiser @pavolloffay

[black-adder]

makes sense, given the refactor was technically a breaking change, anything to make the transition easier is worth it.

[pavolloffay]

+1 on this

[objectiser]

+1