Auto merge of #14978 - shinglyu:inline-flex, r=notriddle

Implemented display: inline-flex

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #14685 (github issue number if applicable).

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- [x] There are tests for these changes
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tests/wpt/metadata-css/css-flexbox-1_dev/html/display_inline-flex_exist.htm.ini

@@ -1,5 +0,0 @@
-[display_inline-flex_exist.htm]
-  type: testharness
-  [CSS Flexible Box Test: display_inline-flex]
-    expected: FAIL
-

tests/wpt/metadata-css/css-flexbox-1_dev/html/flexbox_computedstyle_display-inline.htm.ini

@@ -1,5 +0,0 @@
-[flexbox_computedstyle_display-inline.htm]
-  type: testharness
-  [flexbox | computed style | display: inline-flex]
-    expected: FAIL
-

tests/wpt/metadata-css/css-flexbox-1_dev/html/flexbox_inline.htm.ini

@@ -1,3 +0,0 @@
-[flexbox_inline.htm]
-  type: reftest
-  expected: FAIL

tests/wpt/metadata-css/css-flexbox-1_dev/html/ttwf-reftest-flex-inline.htm.ini

@@ -1,3 +0,0 @@
-[ttwf-reftest-flex-inline.htm]
-  type: reftest
-  expected: FAIL