Backmerge: #2000 Exporting a CDX file to ChemDraw loses information about charge on atoms

[AliaksandrDziarkach]

Backmerge to master Add charge to labes. Fix UTs

Backmerge request

• [ ] PR name follows the pattern Backmerge: #1234 – issue name
• [ ] PR is linked with the issue
• [ ] base branch (master or release/xx) is correct
• [ ] code contains only backmerge changes