Try a more compact save state indicator

[jasmussen]

This PR does three things:

1. It makes the "Save Draft" label just say "Save" on mobile
2. It tightens the space around the editor mode switch, while keeping the hit area the same
3. It adds negative margin to the "Saved" dashicon so it visually aligns with the text

Screenshots:

[codecov]

Codecov Report

Merging #2445 into master will increase coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2445      +/-   ##
==========================================
+ Coverage   26.51%   26.64%   +0.12%     
==========================================
  Files         158      158              
  Lines        4853     5074     +221     
  Branches      816      887      +71     
==========================================
+ Hits         1287     1352      +65     
- Misses       3013     3115     +102     
- Partials      553      607      +54

Impacted Files	Coverage Δ
editor/header/saved-state/index.js	85.71% <ø> (ø)	⬆️
blocks/editable/index.js	9.57% <0%> (-1.31%)	⬇️
blocks/api/paste/normalise-blocks.js	95.74% <0%> (-0.26%)	⬇️
editor/sidebar/table-of-contents/item.js	0% <0%> (ø)	⬆️
blocks/api/paste/strip-attributes.js	100% <0%> (ø)	⬆️
editor/sidebar/table-of-contents/index.js	0% <0%> (ø)	⬆️
blocks/api/paste/strip-wrappers.js	100% <0%> (ø)	⬆️
blocks/api/paste/index.js	100% <0%> (ø)	⬆️
blocks/editable/format-toolbar/index.js	10% <0%> (+2.5%)	⬆️
editor/utils/url.js	66.66% <0%> (+66.66%)	⬆️

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[jasmussen]

Merging this. Let's consider separately exploring augmenting tests to account for viewport widths.