remove old integration testing code

[khieta]

Description of changes

• Deleted the cedar-integration-tests/ folder and cedar-policy/integration_testing.rs file.
• Some small updates to the README, CHANGELOG, and Cargo.toml to reflect the new change.

Issue #, if available

Resolves #820

Checklist for requesting a review

The change in this PR is (choose one, and delete the other options):

• A breaking change requiring a major version bump to cedar-policy (e.g., changes to the signature of an existing API).

I confirm that this PR (choose one, and delete the other options):

• Updates the "Unreleased" section of the CHANGELOG with a description of my change (required for major/minor version bumps).

I confirm that cedar-spec (choose one, and delete the other options):

• Does not require updates because my change does not impact the Cedar formal model or DRT infrastructure.

[khieta]

Looks like the size of the commit will make reviewing difficult. Here's the actual important part of the diff:

• README.md

 * [cedar-policy-core](./cedar-policy-core) : Internal crate containing the Cedar parser and evaluator
 * [cedar-policy-validator](./cedar-policy-validator) : Internal crate containing the Cedar validator
 * [cedar-policy-formatter](./cedar-policy-formatter) : Internal crate containing an auto-formatter for Cedar policies
-* [cedar-integration-tests](./cedar-integration-tests) : Crate containing integration tests
+* [cedar-testing](./cedar-testing) : Internal crate containing integration testing code

• cedar-policy/CHANGELOG.md

 - Overhauled the FFI interface in the `frontend` module, and renamed it to
   `ffi`; see #757. (#760, #793, #794, #800, #824, more coming)
 - Much richer error information in the FFI interface (#800)
-- Deprecated the integration testing harness code. It will be removed from the
-  `cedar-policy` crate in the next major version.
 - Removed unnecessary lifetimes from some validation related structs (#715)
 - Made `is_authorized` and `validate` functions in the frontend public, as well as their related structs: `AuthorizationAnswer`, `AuthorizationCall`, `Vali
dationCall`, `ValidationSettings`, `ValidationEnabled`, `ValidationError`, `ValidationWarning`, `ValidationAnswer`. (#737)
 - Changed policy validation to reject comparisons and conditionals between
   record types that differ in whether an attribute is required or optional.
 
+### Removed
+
+- Removed integration testing harness from the `cedar-policy` crate. It is now
+  in an internal crate, allowing us to make semver incompatible changes. (#857)
+
 ## [3.2.0] - Coming Soon
 
 ### Added
@@ -51,6 +54,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   report the precise source location where the unknown type was encountered.
   Error for invalid use of an action now includes a source location containing
   the offending policy. (#802, #808, resolving #522)
+- Deprecated the integration testing harness code. It will be removed from the
+  `cedar-policy` crate in the next major version. (#707)

• cedar-policy/Cargo.toml

 heap-profiling = ["dep:dhat"]
 corpus-timing = []
 
-integration_testing = []
-
 # Experimental features.
 # Enable all experimental features with `cargo build --features "experimental"`
 experimental = ["partial-eval", "permissive-validate", "partial-validate"]
@@ -58,17 +56,6 @@ wasm = ["serde-wasm-bindgen", "tsify", "wasm-bindgen"]
 crate_type = ["rlib", "cdylib"]
 
 [dev-dependencies]
-# Hack to enable the `integration_testing` feature for the `Cedar` integration
-# tests without enabling it by default for ordinary consumers of `Cedar`. The
-# `default-features = false` stops this dependency from forcibly enabling the
-# default features of `Cedar`, leaving the default features to be controlled by
-# the ordinary `--no-default-features` flag of `cargo test`. See
-# https://github.com/rust-lang/cargo/issues/2911#issuecomment-1483256987 for
-# more information. That issue also tracks a real solution to the problem that
-# could replace this hack.
-cedar-policy = { path = ".", default-features = false, features = [
-    "integration_testing",
-] }
 cool_asserts = "2.0"
 criterion = "0.5"
 globset = "0.4"

• cedar-policy/src/lib.rs

mod prop_test_policy_set;
 mod tests;
-
-#[cfg(feature = "integration_testing")]
-#[deprecated(since = "3.2.0", note = "please use the `cedar-testing` crate instead")]
-pub mod integration_testing;

[khieta]

CI SemVer failure is expected. Downstream DRT failures are because we're (unnecessarily) depending on the integration_testing flag downstream. This should be an easy fix.