fix: regression of imageInfo initialization for categorizing environments by label in metadata

[lizable]

This PR fixes regression issue of missing categories in "environment select UI" inside session-launcher.
All of image except custom image, which is without description in metadata, should be grouped with the title defined in
metadata.json.
For more details, please look through the code below.

backend.ai-webui/src/components/backend-ai-resource-broker.ts

Lines 1096 to 1108 in fe8209a

	this.supportImages[supportsKey] = this.imageInfo[imageName] || {
	name: 'Custom Environments',
	description: 'Custom-built images.',
	group: 'Custom Environments',
	tags: [],
	label: [
	{
	category: 'Custom',
	tag: 'Custom',
	color: 'black',
	},
	],
	};

After	before

Checklist: (if applicable)

• Mention to the original issue
• Documentation
• Minimum required manager version
• Specific setting for review (eg., KB link, endpoint or how to setup)
• Minimum requirements to check during review
• [] Test case(s) to demonstrate the difference of before/after

[inureyes]

LGTM

[inureyes]

LGTM