Add strategy for customizing ID/TIMESTAMP headers

Introduce MessageHeaderInitializer strategy for initializing a
MessageHeaderAccessor.

Add IdTimestampMessageHeaderInitializer implementation that provides
control over ID and timestamp header generation.

Disable ID and timestamp by default in SimpMessageHeaderAccessor and
therefore its sub-class StompHeaderAccessor.

Issue: SPR-11468
Use strategy for customizing ID/TIMESTAMP generation

Issue: SPR-11468