PGdoc: add missing ID attribute to create_subscription.sgml

Dear hackers, (CC: reviewers of copy-binary patch)

This is an follow-up thread of [1]. PSA patch that adds an attributes.

By ecb6965, an XML ID attribute is added only one varlistentry in create_subscription.sgml.
But according to the commit 78ee60 and related discussions [2], [3], it is worth
adding ID attribute to other entries. This patch adds them.

Moreover, I have added some references to parameters from pre-existing documents.
Only entries that are referred from other files have XREFLABEL attribute.

Basically I detected the to-be-added position by:

1. Grepped subscription options, e.g. <literal>two_phase</literal>
2. Found a first place of above detection in each sgml files.
3. Replaced them link, e.g. <xref linkend="sql-createsubscription-with-two-phase"/>.

"XXX = YYY" style was not replaced because there are few links of its style for now.

[1]: https://www.postgresql.org/message-id/flat/CAGPVpCQvAziCLknEnygY0v1-KBtg+Om-9JHJYZOnNPKFJPompw@mail.gmail.com
[2]: https://www.postgresql.org/message-id/CAB8KJ=jpuQU9QJe4+RgWENrK5g9jhoysMw2nvTN_esoOU0=a_w@mail.gmail.com
[3]: https://www.postgresql.org/message-id/3bac458c-b121-1b20-8dea-0665986faa40@gmx.de

Best Regards,
Hayato Kuroda
FUJITSU LIMITED