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

**Use case**
People are used to Postgres.
{
protected:
    const char * getName() const override { return "order by expression"; }
    bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override;
};
class ParserKeyValuePair : public IParserBase
{
protected:
    const char * getName() const override { return "key-value pair"; }
    bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override;
};
class ParserKeyValuePairsList : public IParserBase
{
protected:
    const char * getName() const override { return "list of pairs"; }
    bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override;
};
class ParserTTLExpressionList : public IParserBase
{
protected:
    const char * getName() const override { return "ttl expression"; }
    bool parseImpl(Pos & pos, ASTPtr & node, Expected & expected) override;
};
}