Feature: Support for characteristic format descriptors.

[Singh-Sumeet]

The MR aims to add:

1. Support for one or more than one characteristic format descriptors for each characteristic.
2. Support for host add characteristic aggregate format descriptor if multiple cpfds are present.
3. Relevant macros taken from BT SIG Assigned Numbers specification.

[Singh-Sumeet]

@sjanc Please TAL

[sjanc]

CI didn't kick in, could you rebase to trigger it?