[core] Add dynamic IconNext component

[ggdouglas]

Third of three PRs splitting up #8065, stacked on #8175. Adds the dynamic IconNext component and its runtime icon loader, and strengthens the typing of next icon names.

What's here

• IconNext (@blueprintjs/core) renders a next-gen icon from a string name, loading its paths asynchronously on first use (autoLoad, on by default). It also accepts an element for passthrough, and switches between outlined (default) and filled variants, falling back to outlined when an icon has no filled variant.
• IconsNext runtime loader + defaultNextIconPathsLoader (@blueprintjs/icons/next) cache loaded paths and dynamically import the generated paths/ chunk. The component generator now also emits these path modules, so the static and dynamic pipelines share one generator.
• BlueprintIconsNext is a string-literal union of every next icon name, generated from the manifest. It replaces the old string-based NextIconName (kept as an alias), so passing an unknown name to IconNext or IconsNext.load is now a compile error.
• IconNextNames is a PascalCase-keyed name object (IconNextNames.Play === "play"), the next-gen counterpart to IconNames.

How to use

import { IconNext } from "@blueprintjs/core";
import { IconNextNames } from "@blueprintjs/icons/next";

<IconNext icon="play" />
<IconNext icon={IconNextNames.Pause} variant="filled" size={24} />

Stack

0. Base PR ([icons] Add opt-in next-gen static icon components #8065)
1. assets + manifests ([icons] Add next-generation icon assets and manifests #8174)
2. static icon components ([icons] Add static @blueprintjs/icons/next icon components #8175)
3. static icon docs ([docs] Add next-icons documentation page #8182)
4. (this PR) dynamic IconNext component

[blueprint-previews]

[core] Add dynamic IconNext component and typed next icon names

Build artifact links for this commit: documentation | landing | table | demo | storybook

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[blueprint-previews]

[docs] Add IconNext documentation page and example

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[blueprint-previews]

[docs] Add IconNext documentation page and example

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Description

[core] Add dynamic IconNext component

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Type (Select exactly one)

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• Improvement (Improving existing functionality)
• Fix (Fixing an issue with existing functionality)
• Break (Creating a new major version by breaking public APIs)
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• Migration (Automatically moving data/functionality to a new system)

Description

[core] Add dynamic IconNext component

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[blueprint-previews]

Reconcile IconNextName after static/dynamic merge

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[blueprint-previews]

Reconcile IconNextName after static/dynamic merge

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[blueprint-previews]

wip

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