`INTERVAL '1 hour'` should be equivalent to `INTERVAL 1 HOUR`

**Use case**
People are used to Postgres.
#include <boost/algorithm/string.hpp>
#include "ASTColumnsMatcher.h"
#include <Interpreters/StorageID.h>
namespace DB
{
namespace ErrorCodes
{
    extern const int SYNTAX_ERROR;
    extern const int LOGICAL_ERROR;
}
bool ParserArray::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
{
    ASTPtr contents_node;
    ParserExpressionList contents(false);
    if (pos->type != TokenType::OpeningSquareBracket)
        return false;
    ++pos;
    if (!contents.parse(pos, contents_node, expected))
        return false;
    if (pos->type != TokenType::ClosingSquareBracket)
        return false;
    ++pos;
    auto function_node = std::make_shared<ASTFunction>();
    function_node->name = "array";
    function_node->arguments = contents_node;
    function_node->children.push_back(contents_node);
    node = function_node;
    return true;
}
bool ParserParenthesisExpression::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)