fix: fetch quotes when src amount's decimals are greater than token's

[micaelae]

Description

Related issues

Fixes: https://consensyssoftware.atlassian.net/browse/MMS-1840

Manual testing steps

1. Select optimism USDC as src token
2. Select Polygon USDC as destination
3. Type in 10.0000007
4. Quotes should be fetched
5. Try typing/pasting in other invalid inputs like 1abc,. or .1.1.1
6. Input field should only reflect valid parts of the amount

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I've followed MetaMask Contributor Docs and MetaMask Extension Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[metamaskbot]

Builds ready [39fbe7b]

• builds: chrome, firefox
• builds (flask): chrome, firefox
• builds (MMI): chrome
• builds (test): chrome, firefox
• builds (test-flask): chrome, firefox
• build viz: Build System
• mv3: Bundle Size Stats
• mv2: E2e Actions Stats
• storybook: Storybook
• typescript migration: Dashboard
• all artifacts
• bundle viz:

  • background: 0, 1, 2, 3, 4, 5, 6, 7
  • common: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • ui: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13
  • content-script: 0
  • offscreen: 0

Page Load Metrics (1725 ± 80 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	1447	2163	1726	167	80
		domContentLoaded	1436	2106	1692	157	75
		load	1448	2165	1725	167	80
		domInteractive	26	108	44	24	11
		backgroundConnect	12	83	36	25	12
		firstReactRender	16	96	44	26	12
		getState	5	65	17	18	9
		initialActions	0	0	0	0	0
		loadScripts	1045	1645	1253	141	68
		setupStore	7	66	17	19	9
		uiStartup	1606	2406	2001	204	98

Bundle size diffs

• background: 0 Bytes (0.00%)
• ui: 292 Bytes (0.00%)
• common: 0 Bytes (0.00%)