`Kernel#class` can't possibly be called on an hidden object,
hence we don't need to check for `klass == 0`.

```
compare-ruby: ruby 3.5.0dev (2025-08-30T01:45:42Z obj-class 01a57bd6cd) +YJIT +PRISM [arm64-darwin24]
built-ruby: ruby 3.5.0dev (2025-08-30T10:21:10Z obj-class b67c16c477) +YJIT +PRISM [arm64-darwin24]

|           |compare-ruby|built-ruby|
|:----------|-----------:|---------:|
|obj        |     445.217|   642.446|
|           |           -|     1.44x|
|extended   |     136.826|   117.974|
|           |       1.16x|         -|
|singleton  |     166.269|   166.695|
|           |           -|     1.00x|
|immediate  |     380.243|   515.775|
|           |           -|     1.36x|
```

* YJIT: Replace Array#each only when YJIT is enabled

* Add comments about BUILTIN_ATTR_C_TRACE

* Make Ruby Array#each available with --yjit as well

* Fix all paths that expect a C location

* Use method_basic_definition_p to detect patches

* Copy a comment about C_TRACE flag to compilers

* Rephrase a comment about add_yjit_hook

* Give METHOD_ENTRY_BASIC flag to Array#each

* Add --yjit-c-builtin option

* Allow inconsistent source_location in test-spec

* Refactor a check of BUILTIN_ATTR_C_TRACE

* Set METHOD_ENTRY_BASIC without touching vm->running

The examples of chaining for other methods, such as #tap have the dot at
the start of the line, while #then has it at the end of the previous
line. Updated this to have consistent style in Kernel docs.