Proposals page performance under stress test

[damian-molinski]

Summary

We need to make sure ProposalsPage is a optimised as possible

Description

Under heavy load ProposalsPage does not feel smooth

Subtask List

• Measure where time is spent while ProposalsPage is shown. Spot what we can improve and add finding to Improvements List

Depending on finding from previous task

• Create standalone sub-tasks (if problem requires more investigation)
• Create PR per improvement found and measure gains.

Improvements List

• TODO

[damian-molinski]

Implemented in #3641