script: Add presentation attributes as part of a single PropertyDeclarationBlock (servo#38684)

Instead of making a block for each attribute, use a single block as
described in a `FIXME` comment by @emilio. This also switch to using
`map` and `and_then` in more places to make the code a bit more concise.

Testing: This should not change behavior other than to incraese
efficiency a
bit and is thus covered by existing tests.

Signed-off-by: Martin Robinson <[email protected]>

Author: mrobinson