Auto merge of #58403 - eddyb:requalify, r=oli-obk

rustc_mir: split qualify_consts' "value qualification" bitflags into separate computations.

Prerequisite for computing those bits through a dataflow algorithm ~~(which I might do in this PR later)~~.

This PR should not change behavior overall, other than treating `simd_shuffle*` identically to `#[rustc_args_required_const]` (maybe we should just have `#[rustc_args_required_const]` on the intrinsic imports of `simd_shuffle*`? cc @gnzlbg)

cc @oli-obk @alexreg

Cargo.lock

@@ -2822,7 +2822,6 @@ name = "rustc_mir"
 version = "0.0.0"
 dependencies = [
  "arena 0.0.0",
- "bitflags 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "byteorder 1.2.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "either 1.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "graphviz 0.0.0",

src/librustc_mir/Cargo.toml

@@ -11,7 +11,6 @@ crate-type = ["dylib"]
 
 [dependencies]
 arena = { path = "../libarena" }
-bitflags = "1.0"
 either = "1.5.0"
 dot = { path = "../libgraphviz", package = "graphviz" }
 log = "0.4"