[BYOC][ETHOSN] Introduce further operator support (#6355)

[BYOC][ETHOSN] Introduce further operator support (#6355)

* [BYOC][ETHOSN] Introduce further operator support

This PR introduces support for the following operators:
 - Quantized Fully Connected
 - Quantized Addition
 - Depth-to-space
 - Max/Avg Pool 2D
 - Quantized Relu (Clip)
 - Reshape
 - Quantized Sigmoid

Co-authored-by: Leo Blonk <Leo.Blonk@arm.com>
Co-authored-by: Tristan O'Connor <tristan.oconnor@arm.com>
Co-authored-by: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
* Skip tf imports if not available

Change-Id: I11bcf4a78014fa63e7b8e3b0cb00eecfd6cb7760

* ethos -> ethosn

Change-Id: I1fb1a11d0765f6d69f04c24b9c24e08665b8af6a

* Reduce random testing in test_addition

Change-Id: Id06063a0a0cf5f01356df23dc5d4bbbcb47cfa99

* Reduce random testing in test fullyconnected

Change-Id: I330408dfabc4bd804373f100581ce909ff724052

* Fix dumb mistake with rename

Change-Id: I2c5007be485b323116a0e8bab0f9106ea5ec834b

* Added comments to update the hashes in network tests when necessary

Change-Id: I13828c918c959daa492b9ed942a882c86d6690d1

* Fix github name

Change-Id: Idaa70ab9c2ec8db2828d51d15e7c23f28670ec82

* Use black formatting

Change-Id: I538171bd547a16395bef155a1dad28e8b3e347f2

Co-authored-by: Leo Blonk <Leo.Blonk@arm.com>
Co-authored-by: Tristan O'Connor <tristan.oconnor@arm.com>
Co-authored-by: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>