fix: add fallback method for currency formatter in useFiatFormatter hook

[OGPoyraz]

Description

This PR goal is to add a fallback for unknown currency formats to render it ${amount} ${currency} format.

Related issues

Fixes: #24558

Manual testing steps

1. Go to Settings > General
2. Change your currency to Storj
3. Start a send transaction on Ethereum with any value
4. MM doesn't crash and shows amount storj

Screenshots/Recordings

Before

After

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Pre-merge reviewer checklist

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[digiwand]

Nice! Lgtm

[metamaskbot]

Builds ready [ff37d1c]

• builds: chrome, firefox
• builds (beta): chrome
• builds (flask): chrome, firefox
• builds (MMI): chrome, firefox
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Background Module Init Stats
• mv3: UI Init Stats
• mv3: Module Load Stats
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• code coverage: Report
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8
  • content-script: 0
  • ui: 0, 1, 10, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (892 ± 542 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	62	170	97	29	14
		domContentLoaded	9	34	15	6	3
		load	50	2569	892	1129	542
		domInteractive	9	34	15	6	3

Bundle size diffs

• background: 0 Bytes (0.00%)
• ui: 45 Bytes (0.00%)
• common: 0 Bytes (0.00%)