Add SurrealDB as build-in target and for internal storage

[martinschaer]

This PR:

• adds SurrealDB as al alternative DB for the internal storage
• adds SurrealDB as a built-in target (supports vector index with HNSW)

Missing:

• test graph nodes/edges
• support for full-text search indexes

To run the example examples/text_embedding_surrealdb:

• Run SurrealDB with: surreal start -u root -p secret
• Create .env file based on the .env.example

Resulting contents in cocoindex_setup_metadata:

[
	{
		flow_name: 'TextEmbedding',
		id: cocoindex_setup_metadata:TextEmbedding__FlowMetadata__7b8b2cb83a44fca258958d85f88051e474fbcf0d5b0751f05961b3b16df60ee28e4b2e845396151a10ed6ba965c588f2cc97a8bf17f78c30a202e5d154206f76,
		resource_type: 'FlowMetadata',
		staging_changes: [],
		state: {
			features: [
				'fast_fingerprint'
			],
			last_source_id: 1,
			last_target_id: 1,
			sources: {
				documents: {
					key_schema: {
						kind: 'Str'
					},
					keys_schema: [
						{
							kind: 'Str'
						}
					],
					source_id: 1,
					source_kind: 'LocalFile'
				}
			}
		}
	},
	{
		flow_name: 'TextEmbedding',
		id: cocoindex_setup_metadata:TextEmbedding__Target_SurrealDB__56a92c78862a976e7271524fd5587d99a6e4a2880e4b8fd4cd93bdb6efa77f4001f902f1799d87650e8cc078f29304a95126e9e497af691d441dcb7f9e2d5d7e,
		key: {
			connection: {
				key: 'SurrealDBConnection'
			},
			table_name: 'Chunk'
		},
		resource_type: 'Target:SurrealDB',
		staging_changes: [],
		state: {
			common: {
				key_type: [
					{
						kind: 'Str'
					},
					{
						kind: 'Range'
					}
				],
				max_schema_version_id: 1,
				schema_version_id: 1,
				setup_by_user: false,
				target_id: 1
			},
			state: {
				vector_indexes: {
					embedding: {
						field_name: 'embedding',
						field_type: 'F32',
						metric: 'CosineSimilarity',
						vector_size: 1536
					}
				}
			}
		}
	},
	{
		flow_name: 'TextEmbedding',
		id: cocoindex_setup_metadata:TextEmbedding__TrackingTable__7b8b2cb83a44fca258958d85f88051e474fbcf0d5b0751f05961b3b16df60ee28e4b2e845396151a10ed6ba965c588f2cc97a8bf17f78c30a202e5d154206f76,
		resource_type: 'TrackingTable',
		staging_changes: [],
		state: {
			has_fast_fingerprint_column: true,
			table_name: 'TextEmbedding__cocoindex_tracking',
			version_id: 1
		}
	},
	{
		flow_name: 'TextEmbedding',
		id: cocoindex_setup_metadata:TextEmbedding____FlowVersion__7b8b2cb83a44fca258958d85f88051e474fbcf0d5b0751f05961b3b16df60ee28e4b2e845396151a10ed6ba965c588f2cc97a8bf17f78c30a202e5d154206f76,
		resource_type: '__FlowVersion',
		staging_changes: [],
		state: 1
	}
]