The Value interface exposes values to the debugger.
Variables are named values.
VariableContainer is a collection of Variables.

Bug: b/145351270
Change-Id: Iae3749447554977f84bfc6e58f37b52aa6ed262f
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38893Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>