feat: add sentry__value_from_msgpack

[jpnurmi]

The opposite of sentry_value_to_msgpack. For offline caching of Crashpad envelopes.

Required for:

• WIP: feat(crashpad): offline caching #1493

Example usage for msgpacked crashpad attachments (__sentry-event and __sentry-breadcrumbsN):

sentry-native/src/backends/sentry_backend_crashpad.cpp

Lines 436 to 447 in ff864c4

	static sentry_value_t
	read_msgpack_file(const sentry_path_t *path)
	{
	size_t size;
	char *data = sentry__path_read_to_buffer(path, &size);
	if (!data) {
	return sentry_value_new_null();
	}
	sentry_value_t value = sentry__value_from_msgpack(data, size);
	sentry_free(data);
	return value;
	}

#skip-changelog (internal)

[github-actions]

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against 83511fb

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable Autofix in the Cursor dashboard.}