Bugfix: draw template with matrix parameter

[albi3ro]

Bugfix for Issue #1916

Due to the new QNode expansion settings, the qnode tape has unexpanded templates, which the current text circuit drawer was unable to handle. This bugfix generalizes the treatment of matrix parameters.

This code was previously raising an error:

import pennylane as qml
from pennylane import numpy as np

dev = qml.device('default.qubit', wires = 1)

@qml.qnode(dev)
def circuit():
    qml.AmplitudeEmbedding(np.array([0,1]), wires=0)
    return qml.state()
                        
print(qml.draw(circuit)())

But now gives:

 0: ──AmplitudeEmbedding(M0)──┤ State 
M0 =
[0.+0.j 1.+0.j]

[albi3ro]

This line was from a merge remnant and the actual full entry is below, so I tidied it up.

[codecov]

Codecov Report

Merging #1917 (64de6b4) into master (c631726) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1917   +/-   ##
=======================================
  Coverage   98.83%   98.83%           
=======================================
  Files         222      222           
  Lines       16979    16979           
=======================================
  Hits        16781    16781           
  Misses        198      198           

Impacted Files	Coverage Δ
...ennylane/circuit_drawer/representation_resolver.py	99.36% <100.00%> (ø)

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