Add HTML ids for object definitions in the formatted specification (#1174)

* Remove redundant call to resolve-allof

All of the callers to resolve-additional-types already call resolve-allof (or
if not, they should), so this is redundant.

* Update `resolve-additional-types` to take a dict

I want to add more params to this, so first make it take a dict.

* `render-object-table`: take a "title" rather than a "caption"

... which means we can use the result from resolve-additional-types directly.

* render-object-table: support adding an anchor to generated tables.

* resolve-additional-types: generate an id for each returned type

* render-event: pass an anchor_base into resolve-additional-types

This means that it will generate an anchor for each type, whihc will then be
passed into render-object-table and used as an `id` for the table.

* render-operation: pass an anchor_base into resolve-additional-types

* newsfiles

changelogs/push_gateway/newsfragments/1174.clarification

@@ -0,0 +1 @@
+Add HTML anchors for object definitions in the formatted specification.