rgw: make a configurable size for requests with xml params

rgw: make a configurable size for requests with xml params

We currently read all user input for a few apis accepting xml, avoid
doing this and error out early, most s3 apis limit to about 1000 xml
entries, make this configurable via a new config param,
`rgw_max_put_param_size` defaulting to 1MB. Also modified
`rgw_rest_read_all_input` with an additional param to not allow for
chunked uploads, though we error out in a better way by responding with
content length required rather than S3's 501 if chunked is set.

This also adds the same behavior in RGWPutCORS reusing
`rgw_rest_read_all_input`, and using a data_deleter to manage the char*

Signed-off-by: Abhishek Lekshmanan <abhishek@suse.com>
rgw: rgw_rest_s3: make PUT CORS accept only a configured max input

Signed-off-by: Abhishek Lekshmanan <abhishek@suse.com>