Show pull specific flags in pull request page flags selector

[RulaKhaled]

Problem: It is confusing to be able to filter pull flags tab using flags that don’t belong to the PR, we're sending pointless requests to the backend where we can limit the calls to send only useful requests that we can actually make use of flags filter in.

Solution: Show PR specific flags in the pull request page flags selector

we can either use whatever flags tab is using or add a filter API to accept a pullid and adjust current hook to pass it

you will need to create a separate API issue if you decide to move forward with 2nd option.