SES-1112 - Push notifications for message requests Mk3

[alansley]

Contributor checklist

• [X] I have tested my contribution on these devices:

• Samsung S9+, Android 9 / API 28
• Virtual Pixel 3a, Android 14 / API 34
• Virtual Pixel 3a, Android 9 / API 28

• [X] My contribution is fully baked and ready to be merged as is
• [X] I ensure that all the open issues my contribution fixes are mentioned in the commit message of my first commit using the Fixes #1234 syntax

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Description

Message request push notifications now display, but only a single message request notification per sender to avoid being spammed with message requests. Following clearing of the message requests another message request notification may display (if the user does not specifically accept or decline the message request).

Note: There is a issue where the number of message requests may not be correct, but this will be raised as a separate ticket.