rgw: add DPP's to logging for most ops

rgw: add DPP's to logging for most ops

This commit contains the following major
changes:

- Most log output lines for major ops now have
DoutPrefixProviders.

- Create new macro ldpp_subdout. This macro is meant
as a replacement for lsubdout for headerfiles that
do not define the rgw subsys.

- Changes to RGWObjManifest begin and end iterators.

- Make it so that rgw_dencoder.cc should only contain the
logic related to encoding.

Also add dpp to ldouts and lderr's already using
req_state and replace sync_env/env->dpp's with dpp's

Signed-off-by: Ali Maredia <amaredia@redhat.com>
Signed-off-by: Kalpesh Pandya <kapandya@redhat.com>
Signed-off-by: Casey Bodley <cbodley@redhat.com>