Feature: Support to ask user for authorization

[Singh-Sumeet]

This MR aims to add:

1. Support to ask user for authorization in case of GATT read or write operations.
2. Relevant event handling in bleprph app.

[Singh-Sumeet]

@sjanc Please TAL

[Singh-Sumeet]

@sjanc PTAL

[andrzej-kaczmarek]

@Singh-Sumeet we discussed with @sjanc and we agreed that return value from callback should be used instead of event struct field. we'd also like to have an option in future to make it authorization asynchronous so the return values should be reject, accept, pending - please add appropriate macros for that. reject should be set to 0 so authorization is rejected by default.

[Singh-Sumeet]

Hi @andrzej-kaczmarek , I have made the required changes. I don't understand what you mean by making it "Authorization Asynchronous", but I have created the macro nonetheless.