apply fixes to fromBodyXML and toExternalBodyXML transformers

[lokendersinghft]

This PR fixes little things in fromBodyXML and toExternalBodyXML transformers.

from-bodyxml

• Added support for newer body XML inputs, including h5/h6 headings
• data-layout parsing for ClipSet instead of data-layout-width
• Content and Article links should use title attribute instead of dataTitle
• inline formatting passthrough, b, sup, sub, u, i, del, small
• whitespace-only text node handling,
• flourish layout width defaults to in-line
• flourish sets fragmentIdentifier only when data-fragment-identifier is present, instead of reusing id attribute

to-external-bodyxml

• Improved XML serialization by escaping attribute/text values for links, pull quotes, big numbers, embedded media links, and tweets.
• support for optional external attributes such as data-fragment-identifier on headings, image-set, clip-set, and flourish.
• support for CustomCodeComponent using the current simplified node shape.
• output formatting for self-closing tags (<br/>, <hr/>)
• ClipSet layout output to data-layout.
• support data-fragment-identifier in h tags.

We are also updating CustomCodeComponent and Tweet Go schemas to match body-tree schemas.

JIRA --> https://financialtimes.atlassian.net/browse/UPPSF-6880

[adgad]

I'm guessing this part is temporary, until we add support for super/sub script into the schema?

[lokendersinghft]

I think we can remove them as part of the PRs for super/sub script, and add proper support for them.