This call is unnecessary and wasteful for callers that are building
parallel widget trees, since for those use cases, the caller is
generally going to build the tree synchronously immediately.

This can be useful for offscreen widget trees, where the caller
wants to completely tear down the tree (properly clean up) when
they're done with the tree, to ensure they're not leaving behind
any event listeners that could be registered by child elements
(which could lead to memory leaks and unexpected behavior).

* 8aeccc46a Roll Skia from 62b039b36d4d to e2c9d3c034dc (5 revisions) (flutter/engine#24312)

* 34991bb18 Roll Dart SDK from 02230d7386c7 to 4bd4c2a493e9 (6 revisions) (flutter/engine#24313)

* dcb23ea4e Roll Skia from e2c9d3c034dc to ec04e062f3f5 (5 revisions) (flutter/engine#24316)

* 0e90ebc6d Roll Fuchsia Mac SDK from LHRp0kYRi... to Yyj0Krr1G... (flutter/engine#24319)

* 5c23b54b8 Roll Fuchsia Linux SDK from QJfCXnklY... to cSlRZzm0z... (flutter/engine#24320)

* 204356d57 Roll Skia from ec04e062f3f5 to 7f942e46fda2 (3 revisions) (flutter/engine#24321)

* 7b0735ec7 Roll Dart SDK from 4bd4c2a493e9 to 4740b09e11d4 (2 revisions) (flutter/engine#24323)

* 4e760899e Roll Skia from 7f942e46fda2 to 9e2c50edaaac (1 revision) (flutter/engine#24324)

* 0c56493d8 Roll Skia from 9e2c50edaaac to 140adc676219 (1 revision) (flutter/engine#24326)

* bdb78dd54 Roll Dart SDK from 4740b09e11d4 to f832cd2d0536 (1 revision) (flutter/engine#24328)

* 2488c1f13 Revert "Reland "[metal] Darwin unified external metal textures (#2415… (flutter/engine#24331)

This reverts commit fe003535.