[C-1279] PR activities improvements

[nunoeufrasio]

PR activities in conversations

Currently, within conversation drawers we’re displaying the PR title in almost every type of activity across the timeline. Since the user already has context of which PR the conversation is related to (displayed on top of the drawer), there’s no need to repeat this label in all activities.

Improvement/Solution: Have a simplified label for PR activities within conversations

• Assigned pull request [pull-request-name] to [member-name] > Assigned pull request to [member-name]
• Requested a review for pull request [pull-request-name] from [member-name] > Requested a review from [member-name]
• Reviewed pull request [pull-request-name] > Reviewed pull request
• Merged pull request [pull-request-name] > Merged pull request
• Closed pull request [pull-request-name] > Closed pull request

PS: the same applies to conversation cards within “Conversations” list

---------------

PR activities as single activities (Activities list)

Currently, activity cards of comments to pull requests don't provide context of which PR the comment is related to, user has to open conversation or GH page to get it.

Improvement/solution: Add the PR title on top of the comment within the activity card.

PS: Open/Closed pull request cards should remain the same, displaying the both PR title and body within the card 

_{From SyncLinear.com | C-1279}