(fix: #14521) Browser hangs when QTree is loaded with relatively large data

[hermit99]

What kind of change does this PR introduce?

• Bugfix
• Feature
• Documentation
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

The PR fulfills these requirements:

• It's submitted to the dev branch (or v[X] branch)
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• It's been tested on a Cordova (iOS, Android) app
• It's been tested on an Electron app
• Any necessary documentation has been added or updated in the docs or explained in the PR's description.

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to start a new feature discussion first and wait for approval before working on it)

Other information:
The issue #14521 is mitigated by adding a noTransition prop where tree nodes are not wrapped by QSlideTransition.

This work-around doesn't address QTree's further performance enhancement needs due to the current design & implementation. It seems hard to do so without introducing breaking changes. For example, tree is coupled with nodes, therefore meta, the flat state of tree, is discarded, travelled and rebuilt each time when a node is expanded or ticked, which is too expensive. On a mid-spec PC, rebuilding of 30K nodes tree could take about 200-600ms, causing noticeable lags when expand a parent node.

[rstoenescu]

Thank you for contributing!

[rstoenescu]

This will go into Quasar v2.9.2