Update logic for showing and rendering the “Show unused payees” button

[j-f1]

• The button will now be hidden by default so that users who don’t have any unused payees won’t have to think about it (since we merge by default, unused payees should be pretty rare)
• The number of unused payees will be shown on the button to help understand how much cleanup needs to be done

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[github-actions]

Bundle Stats - desktop-client

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Files count	Total bundle size	% Changed
13	2.34 MB -> 2.34 MB (+6 B)	+0.00%

Changeset

File	Δ	Size
src/components/payees/index.js	📈 +19 B (+0.18%)	10.4 KB -> 10.42 KB

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Asset	File Size	% Changed
static/js/main.js	1.03 MB -> 1.03 MB (+6 B)	+0.00%

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Asset	File Size	% Changed
static/js/457.chunk.js	387.21 KB	0%
static/media/Inter.var.woff2	317.25 KB	0%
static/media/Inter-italic.var.woff2	239.29 KB	0%
static/media/Inter-roman.var.woff2	221.86 KB	0%
static/media/bg.svg	116.73 KB	0%
static/js/reports.chunk.js	20.77 KB	0%
static/js/969.chunk.js	12.94 KB	0%
static/js/resize-observer-polyfill.chunk.js	8.12 KB	0%
static/css/main.css	6.08 KB	0%
index.html	1.68 KB	0%
asset-manifest.json	1.47 KB	0%
static/media/browser-server.js	963 B	0%

[github-actions]

Bundle Stats - loot-core

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Total

Files count	Total bundle size	% Changed
2	1.97 MB	0%

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kcab.worker.js	1016.62 KB	0%
xfo.xfo.kcab.worker.js	1004.04 KB	0%

[biohzrddd]

This looks good and functions as expected. It will also help out my dark theme.

LGTM