[meta] Make more things pub(crate) instead of pub;

This could help the compiler find unused fields/methods. It didn't find any
during this migration.

cranelift/codegen/meta/src/isa/riscv/encodings.rs

@@ -18,7 +18,7 @@ fn enc(inst: impl Into<InstSpec>, recipe: EncodingRecipeNumber, bits: u16) -> En
     EncodingBuilder::new(inst.into(), recipe, bits)
 }
 
-pub struct PerCpuModeEncodings<'defs> {
+pub(crate) struct PerCpuModeEncodings<'defs> {
     pub inst_pred_reg: InstructionPredicateRegistry,
     pub enc32: Vec<Encoding>,
     pub enc64: Vec<Encoding>,

cranelift/codegen/meta/src/isa/x86/encodings.rs

@@ -18,7 +18,7 @@ use crate::shared::Definitions as SharedDefinitions;
 
 use super::recipes::{RecipeGroup, Template};
 
-pub struct PerCpuModeEncodings {
+pub(crate) struct PerCpuModeEncodings {
     pub enc32: Vec<Encoding>,
     pub enc64: Vec<Encoding>,
     pub recipes: Recipes,

cranelift/codegen/meta/src/isa/x86/recipes.rs

@@ -13,7 +13,7 @@ use crate::shared::Definitions as SharedDefinitions;
 /// Helper data structure to create recipes and template recipes.
 /// It contains all the recipes and recipe templates that might be used in the encodings crate of
 /// this same directory.
-pub struct RecipeGroup<'builder> {
+pub(crate) struct RecipeGroup<'builder> {
     /// Memoized format pointer, to pass it to builders later.
     formats: &'builder FormatRegistry,