Function names in linked SMIR JSON should be qualified with crate name

[jberthold]

To avoid name collisions between functions coming from different crates in the linked SMIR JSON, the (human-readable) function names should be qualified with the crate name.

• This name change only affects how users specify --start-symbol, all internal operations in the semantics use the fully-qualified names.
• Unless a specific "main crate" is identified to the linker, users will have to always qualify the function names they use as start symbol with the crate name.