Text changes font after saving (conversion to SVG1.1)

Steps to reproduce:

• open Inkscape
• Make sure preferences "Save SVG1.1 text" is checked
• create text frame with some text
• set the font
• save the file
• open it back
• change the text

What happened?

The text lost some of it's formatting because the text frame which started off as a simple "<text" element, got changed to a "<tspan" that tspan gets removed when editing the whole block which reverts some of the font changes between saves. Depending on what the state of the text element was before saving.

What should have happened?

To be honest, we should save text as SVG2.0 and only ask users to save as 1.1 text optionally. But it should also be much better at preserving the font style when editing text with tspans. The style should be taken from the first tspan the selected text is about to delete when it replaces text.

Inkscape Version and Operating System:

• Inkscape Version: 1.1
• Operating System: Ubuntu
• Operating System version: 20.04