Introduce OpenSSL INI for selecting libctx

[bukka]

This introduces a new INI that will allow fallback to default ctx. The plan is to actually initially use custom libctx only on ZTS by default and keep the default one for non-zts. The reason why it's not done in this PR is to allow CI to test the custom libctx.

In addition custom libctx now loads the config and also legacy provider if LOAD_OPENSSL_LEGACY_PROVIDER defined.

There's been some minor init / globals refactoring done as well.

[Girgias]

You can just use the zend_string APIs which are clearer, and can also do some pointer comparisons if the strings are interned for any reason.

Suggested change

	#if PHP_OPENSSL_API_VERSION >= 0x30000
	const char *name = ZSTR_VAL(new_value);
	if (!strcmp(name, "default")) {
	OPENSSL_G(ctx).libctx = OPENSSL_G(ctx).default_libctx;
	} else if (!strcmp(name, "custom")) {
	OPENSSL_G(ctx).libctx = OPENSSL_G(ctx).custom_libctx;
	} else {
	int err_type;
	if (stage == ZEND_INI_STAGE_RUNTIME) {
	err_type = E_WARNING;
	} else {
	err_type = E_ERROR;
	}
	/* Do not output error when restoring ini options. */
	if (stage != ZEND_INI_STAGE_DEACTIVATE) {
	php_error_docref(NULL, err_type, "OpenSSL libctx \"%s\" cannot be found", name);
	}
	return FAILURE;
	}
	#if PHP_OPENSSL_API_VERSION >= 0x30000
	if (zend_string_equals(new_value, "default")) {
	OPENSSL_G(ctx).libctx = OPENSSL_G(ctx).default_libctx;
	} else if (zend_string_equals(new_value, "custom")) {
	OPENSSL_G(ctx).libctx = OPENSSL_G(ctx).custom_libctx;
	} else {
	int err_type;
	if (stage == ZEND_INI_STAGE_RUNTIME) {
	err_type = E_WARNING;
	} else {
	err_type = E_ERROR;
	}
	/* Do not output error when restoring ini options. */
	if (stage != ZEND_INI_STAGE_DEACTIVATE) {
	php_error_docref(NULL, err_type, "OpenSSL libctx \"%s\" cannot be found", ZSTR_VAL(new_value));
	}
	return FAILURE;
	}

[SakiTakamachi]

Is this used only when stage != ZEND_INI_STAGE_DEACTIVATE?