[SPARK-22666][ML][SQL] Spark datasource for image format

## What changes were proposed in this pull request?

Implement an image schema datasource.

This image datasource support:
  - partition discovery (loading partitioned images)
  - dropImageFailures (the same behavior with `ImageSchema.readImage`)
  - path wildcard matching (the same behavior with `ImageSchema.readImage`)
  - loading recursively from directory (different from `ImageSchema.readImage`, but use such path: `/path/to/dir/**`)

This datasource **NOT** support:
  - specify `numPartitions` (it will be determined by datasource automatically)
  - sampling (you can use `df.sample` later but the sampling operator won't be pushdown to datasource)

## How was this patch tested?
Unit tests.

## Benchmark
I benchmark and compare the cost time between old `ImageSchema.read` API and my image datasource.

**cluster**: 4 nodes, each with 64GB memory, 8 cores CPU
**test dataset**: Flickr8k_Dataset (about 8091 images)

**time cost**:
- My image datasource time (automatically generate 258 partitions):  38.04s
- `ImageSchema.read` time (set 16 partitions): 68.4s
- `ImageSchema.read` time (set 258 partitions):  90.6s

**time cost when increase image number by double (clone Flickr8k_Dataset and loads double number images)**:
- My image datasource time (automatically generate 515 partitions):  95.4s
- `ImageSchema.read` (set 32 partitions): 109s
- `ImageSchema.read` (set 515 partitions):  105s

So we can see that my image datasource implementation (this PR) bring some performance improvement compared against old`ImageSchema.read` API.

Closes #22328 from WeichenXu123/image_datasource.

Authored-by: WeichenXu <[email protected]>
Signed-off-by: Xiangrui Meng <[email protected]>

Author: WeichenXu123

…b/images/kittens/29.5.a_b_EGDP022204.jpg …s/origin/kittens/29.5.a_b_EGDP022204.jpgdata/mllib/images/kittens/29.5.a_b_EGDP022204.jpg renamed to data/mllib/images/origin/kittens/29.5.a_b_EGDP022204.jpg data/mllib/images/kittens/29.5.a_b_EGDP022204.jpg renamed to data/mllib/images/origin/kittens/29.5.a_b_EGDP022204.jpg

@@ -0,0 +1,13 @@
+The images in the folder "kittens" are under the creative commons CC0 license, or no rights reserved:
+https://creativecommons.org/share-your-work/public-domain/cc0/
+The images are taken from:
+https://ccsearch.creativecommons.org/image/detail/WZnbJSJ2-dzIDiuUUdto3Q==
+https://ccsearch.creativecommons.org/image/detail/_TlKu_rm_QrWlR0zthQTXA==
+https://ccsearch.creativecommons.org/image/detail/OPNnHJb6q37rSZ5o_L5JHQ==
+https://ccsearch.creativecommons.org/image/detail/B2CVP_j5KjwZm7UAVJ3Hvw==
+
+The chr30.4.184.jpg and grayscale.jpg images are also under the CC0 license, taken from:
+https://ccsearch.creativecommons.org/image/detail/8eO_qqotBfEm2UYxirLntw==
+
+The image under "multi-channel" directory is under the CC BY-SA 4.0 license cropped from:
+https://en.wikipedia.org/wiki/Alpha_compositing#/media/File:Hue_alpha_falloff.png