[byteorder] Remove byteorder feature and crate dep

Remove the `byteorder` feature and the dependency on the `byteorder`
crate. Replace the `ByteOrder` trait and types which implement it from
the `byteorder` crate with our own native implementations. This allows
us to make some of our functions and methods `const`.

Add `Usize` and `Isize` byte order-aware types.

Closes #438

Cargo.toml

@@ -36,9 +36,11 @@ pinned-nightly = "nightly-2023-10-31"
 features = ["__internal_use_only_features_that_work_on_stable"]
 
 [features]
-default = ["byteorder"]
-
 alloc = []
+# Do not enable this feature; it will cause compilation to fail. It exists to
+# provide more helpful error messages for crates updating from a previous
+# version which provided this feature.
+byteorder = []
 derive = ["zerocopy-derive"]
 simd = []
 simd-nightly = ["simd"]
@@ -50,11 +52,6 @@ __internal_use_only_features_that_work_on_stable = ["alloc", "derive", "simd"]
 [dependencies]
 zerocopy-derive = { version = "=0.7.21", path = "zerocopy-derive", optional = true }
 
-[dependencies.byteorder]
-version = "1.3"
-default-features = false
-optional = true
-
 # The "associated proc macro pattern" ensures that the versions of zerocopy and
 # zerocopy-derive remain equal, even if the 'derive' feature isn't used.
 # See: https://github.com/matklad/macro-dep-test

README.md

@@ -49,15 +49,6 @@ for network parsing.
   the `alloc` crate is added as a dependency, and some allocation-related
   functionality is added.
 
-- **`byteorder`** (enabled by default)
-  Adds the `byteorder` module and a dependency on the `byteorder` crate.
-  The `byteorder` module provides byte order-aware equivalents of the
-  multi-byte primitive numerical types. Unlike their primitive equivalents,
-  the types in this module have no alignment requirement and support byte
-  order conversions. This can be useful in handling file formats, network
-  packet layouts, etc which don't provide alignment guarantees and which may
-  use a byte order different from that of the execution platform.
-
 - **`derive`**
   Provides derives for the core marker traits via the `zerocopy-derive`
   crate. These derives are re-exported from `zerocopy`, so it is not