[runtime] Add an options API. (#32595)

[runtime] Add an options API. (#32595)

* [runtime] Add an options API.

Add a general options API to the runtime, based on the flags API in Google V8:

```https://chromium.googlesource.com/v8/v8.git/+/refs/heads/master/src/flags/```

Supported features:
* Definition of runtime options in a declarative way.
* Options are mapped to C globals.
* BOOL/INT/STRING data types.
* Generic option parsing code.
* Generic usage code.
* Read-only flags for build-time optimization.

This is designed to replace the many option parsing functions in
the runtime, MONO_DEBUG, the many mono_set_... functions etc.

* Fix the build.

Co-authored-by: vargaz <vargaz@users.noreply.github.com>
Co-authored-by: Zoltan Varga <vargaz@gmail.com>