[BUGFIX] SoftReferenceIndex typolink lacks support for title attributes

The SoftReferenceIndex parses and rebuilds typolink tags, but the
support for the title attributes was missing.
This leads to lost title attributes on typolinks in exports from impexp.

Resolves: #56580
Releases: 6.2, 6.1, 6.0, 4.5
Change-Id: I9bf5c02b79ae4c9024322f0da99dcca37b678daa
Reviewed-on: https://review.typo3.org/28083
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Markus Klein
Tested-by: Markus Klein