Enforce limits on tile GPU memory usage (bp #688)

[mergify]

This is an automatic backport of pull request #688 done by Mergify.

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Changes to be committed:
	modified:   common/api/bentleyjs-core.api.md
	modified:   common/api/frontend-devtools.api.md
	modified:   common/api/imodeljs-frontend.api.md
	modified:   common/api/summary/bentleyjs-core.exports.csv
	modified:   common/api/summary/frontend-devtools.exports.csv
	modified:   common/api/summary/imodeljs-frontend.exports.csv
	modified:   common/api/summary/webgl-compatibility.exports.csv
	modified:   common/api/webgl-compatibility.api.md
	new file:   common/changes/@bentley/bentleyjs-core/gpu-memory-limits_2021-01-26-15-27.json
	new file:   common/changes/@bentley/frontend-devtools/gpu-memory-limits_2021-01-26-15-27.json
	new file:   common/changes/@bentley/frontend-devtools/gpu-memory-limits_2021-02-03-23-21.json
	new file:   common/changes/@bentley/hypermodeling-frontend/gpu-memory-limits_2021-01-26-15-27.json
	new file:   common/changes/@bentley/imodeljs-frontend/gpu-memory-limits_2021-01-26-15-27.json
	new file:   common/changes/@bentley/imodeljs-frontend/gpu-memory-limits_2021-02-03-23-21.json
	new file:   common/changes/@bentley/webgl-compatibility/gpu-memory-limits_2021-02-03-23-21.json
	new file:   core/bentley/src/OrderedSet.ts
	modified:   core/bentley/src/bentleyjs-core.ts
	modified:   core/frontend-devtools/README.md
	modified:   core/frontend-devtools/public/locales/en/FrontendDevTools.json
	modified:   core/frontend-devtools/src/FrontEndDevTools.ts
	modified:   core/frontend-devtools/src/frontend-devtools.ts
	new file:   core/frontend-devtools/src/tools/SetGpuMemoryLimitTool.ts
	modified:   core/frontend-devtools/src/widgets/DiagnosticsPanel.ts
	modified:   core/frontend-devtools/src/widgets/MemoryTracker.ts
	new file:   core/frontend-devtools/src/widgets/TileMemoryBreakdown.ts
	modified:   core/frontend/src/DrawingViewState.ts
	modified:   core/frontend/src/IModelApp.ts
	modified:   core/frontend/src/SheetViewState.ts
	modified:   core/frontend/src/ViewManager.ts
	modified:   core/frontend/src/ViewState.ts
	modified:   core/frontend/src/Viewport.ts
	new file:   core/frontend/src/test/tile/LRUTileList.test.ts
	new file:   core/frontend/src/test/tile/TileAdmin.test.ts
	new file:   core/frontend/src/test/tile/ViewportIdSet.test.ts
	modified:   core/frontend/src/tile/ClassifierTileTree.ts
	new file:   core/frontend/src/tile/DisclosedTileTreeSet.ts
	modified:   core/frontend/src/tile/IModelTile.ts
	modified:   core/frontend/src/tile/IModelTileTree.ts
	new file:   core/frontend/src/tile/LRUTileList.ts
	modified:   core/frontend/src/tile/OrbitGtTileTree.ts
	modified:   core/frontend/src/tile/RealityModelTileTree.ts
	modified:   core/frontend/src/tile/RealityTileTree.ts
	modified:   core/frontend/src/tile/Tile.ts
	modified:   core/frontend/src/tile/TileAdmin.ts
	modified:   core/frontend/src/tile/TileTree.ts
	modified:   core/frontend/src/tile/TileTreeReference.ts
	modified:   core/frontend/src/tile/internal.ts
	modified:   core/frontend/src/tile/map/ImageryTileTree.ts
	modified:   core/frontend/src/tile/map/MapTile.ts
	modified:   core/frontend/src/tile/map/MapTileTree.ts
	modified:   core/hypermodeling/src/SectionGraphicsProvider.ts
	modified:   core/webgl-compatibility/src/Capabilities.ts
	modified:   full-stack-tests/core/src/frontend/standalone/tile/TileTree.test.ts
	modified:   full-stack-tests/core/src/frontend/standalone/tile/Unloading.test.ts

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   docs/changehistory/NextVersion.md

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