Add HAR (HTTP Archive) Compatibility

[asg017]

• Export a do table to HAR blob
• Import a HAR file to a do table
• Create HAR in scalar function.

-- add page, creator info into meta column
select writefile('my-archive.har',  http_to_har('select * from archives'));

-- TODO: should support pages?
select * from http_har(readfile('my-archive.har'), 'creator_name');

select writefile('my-archive.har', http_get_har(url));
select writefile('my-archive.har', http_post_har(url, body));
select writefile('my-archive.har', http_do_har(method, url, body));