fix: use gap for Snap UI spacing

[FrederikBolding]

Description

This PR changes the Snap UI renderer to use gap for spacing between elements instead of margin. This is more effective than our previous attempts at normalizing spacing with nested panels etc. The new standard is 8px of gap between everything except panels at the root level which has 16px of gap (at the request of @eriknson). This PR removes all the margins for the existing components.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.72%. Comparing base (be87264) to head (abdc876).
Report is 3 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop   #23369   +/-   ##
========================================
  Coverage    68.72%   68.72%           
========================================
  Files         1105     1105           
  Lines        43250    43250           
  Branches     11562    11562           
========================================
  Hits         29720    29720           
  Misses       13530    13530           

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[metamaskbot]

Builds ready [abdc876]

• 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
  • common: 0, 1, 2, 3, 4, 5, 6
  • content-script: 0
  • contentscript: contentscript
  • disable-console: disable-console
  • policy-load: policy-load
  • sentry-install: sentry-install
  • ui: 0, 1, 10, 11, 2, 3, 4, 5, 6, 7, 8, 9

Page Load Metrics (1126 ± 414 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	76	186	125	37	18
		domContentLoaded	11	90	37	22	10
		load	63	2198	1126	862	414
		domInteractive	11	90	37	22	10

Bundle size diffs

• background: 0 Bytes (0.00%)
• ui: -164 Bytes (-0.00%)
• common: 0 Bytes (0.00%)