Implement BreakCommand for SAPI4, fix eSpeak (#13875)
Summary of the issue:
The BreakCommand is not implemented with SAPI4.
There is also a known issue with eSpeak not supporting the break SSML tag correctly.
Description of user facing changes
Fix pauses being announced correctly when using MathPlayer and SAPI4 or eSpeak.
Description of development approach
For SAPI5 the Pau tag is used to implement the pause.
There is a known issue with eSpeak and the break SSML tag, which has been fixed with a workaround, adding the strength attribute, while we wait for espeak-ng/espeak-ng#1232 to be fixed.
