[C++] Use FetchContent for bundled Abseil #48074
Description
Describe the enhancement requested
Upgrading some dependencies has been quite challenging for the project like abseil / grpc / protobuf:
There has been several attempts and the amount of work is massive because all of them are entangled and upgrading one requires to bump others.
When we upgraded to minimum CMake 3.25 the idea was to migrate our dependency management to FetchContent so we don't have to manually maintain and declare the different targets so those are generated at configure time.
This issue is to track specifically moving abseil to FetchContent as the initial step for the rest of dependencies.
This is still challenging as mixing FetchContent and ExternalProject has some timing problems and requires some workarounds but the idea is to allow this workarounds until we have migrated the rest of dependencies and we can get rid of them.
This is only for moving the dependency to FetchContent, upgrading the dependency can be done afterwards as a separate issue.
Component(s)
C++