Drop 'basic-blocks' feature (#1363)

* All: Drop 'basic-blocks' feature

This makes it so that 'basic-blocks' cannot be disabled and we can
start assuming it everywhere.

* Tests: Replace non-bb filetests with bb version

* Tests: Adapt solver-fixedconflict filetests to use basic blocks

cranelift/wasm/Cargo.toml

@@ -25,14 +25,11 @@ wat = "1.0.7"
 target-lexicon = "0.10"
 
 [features]
-default = ["std", "basic-blocks"]
+default = ["std"]
 std = ["cranelift-codegen/std", "cranelift-frontend/std"]
 core = ["hashbrown", "cranelift-codegen/core", "cranelift-frontend/core"]
 enable-serde = ["serde"]
 
-# Temporary feature that enforces basic block semantics.
-basic-blocks = ["cranelift-codegen/basic-blocks", "cranelift-frontend/basic-blocks"]
-
 [badges]
 maintenance = { status = "experimental" }
 travis-ci = { repository = "bytecodealliance/cranelift" }