feat: improve xchain swaps slippage settings with decimals and warnings

[ghgoodreau]

Description

The slippage settings for xchain transactions was not allowing users to input a decimal (i.e. 0.5%), only whole numbers (0, 1, so on...). It also did not display a warning for low slippage settings. This addresses both by allowing the user to input decimal numbers, and displaying a warning when the custom slippage is set to <0.5% in the settings modal.

Related issues

Fixes: https://consensyssoftware.atlassian.net/browse/MMS-1830

Manual testing steps

1. Go to the xchain swaps transaction preparation page.
2. Edit slippage settings.
3. Notice decimals are now allowed, and a warning is displayed with low slippage.

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.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[metamaskbot]

Builds ready [25483db]

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

Page Load Metrics (1627 ± 64 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	245	2052	1571	332	159
		domContentLoaded	1380	2038	1598	131	63
		load	1389	2047	1627	132	64
		domInteractive	24	94	38	21	10
		backgroundConnect	8	76	29	22	11
		firstReactRender	15	70	40	23	11
		getState	5	90	20	21	10
		initialActions	0	1	0	0	0
		loadScripts	1004	1640	1197	127	61
		setupStore	6	52	12	13	6
		uiStartup	1610	2276	1840	157	76

Bundle size diffs

• background: 0 Bytes (0.00%)
• ui: 291 Bytes (0.00%)
• common: 0 Bytes (0.00%)