Add LowerBound and UpperBound kernels

[ahmedsabie]

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This change is 

[lina128]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @ahmedsabie and @pyu10055)

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tfjs-core/src/ops/lower_bound.ts line 72 at r1 (raw file):

function lowerBound_(
    sortedSequence: Tensor|TensorLike, values: Tensor|TensorLike): Tensor {
  return searchSorted_(sortedSequence, values, 'left');

Should we just call searchSorted op?

Code quote:

searchSorted_(sortedSequence, values, 'left');

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tfjs-core/src/ops/upper_bound.ts line 59 at r1 (raw file):

function upperBound_(
    sortedSequence: Tensor|TensorLike, values: Tensor|TensorLike): Tensor {
  return searchSorted_(sortedSequence, values, 'right');

Same, call the op.

Code quote:

searchSorted_(sortedSequence, values, 'right')

[pyu10055]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @ahmedsabie)

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tfjs-core/src/ops/lower_bound.ts line 52 at r1 (raw file):

 *
 * const seq = tf.tensor1d([0, 3, 9, 10, 10]);
 * values = tf.tensor1d([0, 4, 10]);

the snippet test is failing:

const values

same for the one below

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tfjs-core/src/ops/upper_bound.ts line 46 at r1 (raw file):

 * ```js
 * const seq = tf.tensor1d([0, 3, 9, 10, 10]);
 * values = tf.tensor1d([0, 4, 10]);

const values