Fix: Font Weight and Style don't work independently on global styles.

[jorgefilipecosta]

On global styles currently, font-weight and style are not independent contrarily to what happens at the block level. This PR fixes the issue.

How has this been tested?

I added "__experimentalFontWeight": true, to packages/block-library/src/heading/block.json.
I verified the Font Weight UI was available for headings on the heading block global styles panel.

[github-actions]

Size Change: +25 B (0%)

Total Size: 1.21 MB

Filename	Size	Change
build/edit-site/index.js	24.7 kB	+25 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
build/a11y/index.js	1.14 kB	0 B
build/annotations/index.js	3.81 kB	0 B
build/api-fetch/index.js	3.42 kB	0 B
build/autop/index.js	2.83 kB	0 B
build/blob/index.js	665 B	0 B
build/block-directory/index.js	8.72 kB	0 B
build/block-directory/style-rtl.css	943 B	0 B
build/block-directory/style.css	942 B	0 B
build/block-editor/index.js	128 kB	0 B
build/block-editor/style-rtl.css	11.2 kB	0 B
build/block-editor/style.css	11.2 kB	0 B
build/block-library/editor-rtl.css	9.07 kB	0 B
build/block-library/editor.css	9.07 kB	0 B
build/block-library/index.js	149 kB	0 B
build/block-library/style-rtl.css	8.37 kB	0 B
build/block-library/style.css	8.37 kB	0 B
build/block-library/theme-rtl.css	789 B	0 B
build/block-library/theme.css	790 B	0 B
build/block-serialization-default-parser/index.js	1.88 kB	0 B
build/block-serialization-spec-parser/index.js	3.06 kB	0 B
build/blocks/index.js	48.1 kB	0 B
build/components/index.js	171 kB	0 B
build/components/style-rtl.css	15.4 kB	0 B
build/components/style.css	15.4 kB	0 B
build/compose/index.js	10.6 kB	0 B
build/core-data/index.js	15.4 kB	0 B
build/data-controls/index.js	827 B	0 B
build/data/index.js	8.98 kB	0 B
build/date/index.js	31.8 kB	0 B
build/deprecated/index.js	769 B	0 B
build/dom-ready/index.js	571 B	0 B
build/dom/index.js	4.95 kB	0 B
build/edit-navigation/index.js	11.1 kB	0 B
build/edit-navigation/style-rtl.css	881 B	0 B
build/edit-navigation/style.css	885 B	0 B
build/edit-post/index.js	306 kB	0 B
build/edit-post/style-rtl.css	6.49 kB	0 B
build/edit-post/style.css	6.47 kB	0 B
build/edit-site/style-rtl.css	3.93 kB	0 B
build/edit-site/style.css	3.93 kB	0 B
build/edit-widgets/index.js	26.3 kB	0 B
build/edit-widgets/style-rtl.css	3.13 kB	0 B
build/edit-widgets/style.css	3.13 kB	0 B
build/editor/editor-styles-rtl.css	476 B	0 B
build/editor/editor-styles.css	478 B	0 B
build/editor/index.js	43.3 kB	0 B
build/editor/style-rtl.css	3.84 kB	0 B
build/editor/style.css	3.84 kB	0 B
build/element/index.js	4.63 kB	0 B
build/escape-html/index.js	735 B	0 B
build/format-library/index.js	6.74 kB	0 B
build/format-library/style-rtl.css	547 B	0 B
build/format-library/style.css	548 B	0 B
build/hooks/index.js	2.27 kB	0 B
build/html-entities/index.js	623 B	0 B
build/i18n/index.js	3.57 kB	0 B
build/is-shallow-equal/index.js	697 B	0 B
build/keyboard-shortcuts/index.js	2.54 kB	0 B
build/keycodes/index.js	1.94 kB	0 B
build/list-reusable-blocks/index.js	3.1 kB	0 B
build/list-reusable-blocks/style-rtl.css	476 B	0 B
build/list-reusable-blocks/style.css	476 B	0 B
build/media-utils/index.js	5.32 kB	0 B
build/notices/index.js	1.85 kB	0 B
build/nux/index.js	3.42 kB	0 B
build/nux/style-rtl.css	671 B	0 B
build/nux/style.css	668 B	0 B
build/plugins/index.js	2.54 kB	0 B
build/primitives/index.js	1.43 kB	0 B
build/priority-queue/index.js	790 B	0 B
build/redux-routine/index.js	2.84 kB	0 B
build/reusable-blocks/index.js	2.92 kB	0 B
build/rich-text/index.js	13.4 kB	0 B
build/server-side-render/index.js	2.77 kB	0 B
build/shortcode/index.js	1.7 kB	0 B
build/token-list/index.js	1.27 kB	0 B
build/url/index.js	2.84 kB	0 B
build/viewport/index.js	1.86 kB	0 B
build/warning/index.js	1.14 kB	0 B
build/wordcount/index.js	1.22 kB	0 B

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