[codex] Delete function-style apply_patch (#21651)

## Why

`apply_patch` is now a freeform/custom tool. Keeping the old
JSON/function-style registration and parsing path left another way for
models and tests to invoke `apply_patch`, which made the tool surface
harder to reason about.

## What changed

- Removed the `ApplyPatchToolType::Function` variant, JSON `apply_patch`
spec, and handler support for function payloads.
- Kept `apply_patch_tool_type = freeform` as the supported model
metadata path, including Bedrock catalog metadata.
- Migrated `apply_patch` tests and SSE fixtures to custom/freeform tool
calls.

## Verification

- `cargo test -p codex-tools -p codex-protocol -p codex-model-provider`
- `cargo test -p codex-core tools::handlers::apply_patch --lib`
- `cargo test -p codex-core --test all
apply_patch_tool_executes_and_emits_patch_events`
- `cargo test -p codex-core --test all
apply_patch_reports_parse_diagnostics`
- `cargo test -p codex-exec test_apply_patch_tool`
- `just fix -p codex-core`
- `just fix -p codex-tools -p codex-protocol -p codex-model-provider -p
codex-exec`

codex-rs/model-provider/src/amazon_bedrock/catalog.rs

@@ -63,7 +63,7 @@ fn gpt_5_4_cmb_bedrock_model(priority: i32) -> ModelInfo {
         default_reasoning_summary: ReasoningSummary::None,
         support_verbosity: true,
         default_verbosity: Some(Verbosity::Medium),
-        apply_patch_tool_type: Some(ApplyPatchToolType::Function),
+        apply_patch_tool_type: Some(ApplyPatchToolType::Freeform),
         web_search_tool_type: WebSearchToolType::TextAndImage,
         truncation_policy: TruncationPolicyConfig::tokens(/*limit*/ 10_000),
         supports_parallel_tool_calls: true,