Protocols: Update k-point sampling protocols

Based on more extensive tests that also involved a broad range of smearings,
a new set of protocols were devised:

| Name       | Smearing (Ry) | k-points distance (1/A) |
|------------|---------------|-------------------------|
| Precision  |        0.0125 |                    0.10 |
| Efficiency |        0.0200 |                    0.15 |
| Fast       |        0.0275 |                    0.30 |

Here we already update the values in the `PwBaseWorkChain` protocol file. In
a future PR it would be nice to set up a system for protocol aliasing, so
we can also change the names without breaking protocol methods downstream.

src/aiida_quantumespresso/workflows/protocols/pw/base.yaml

@@ -24,7 +24,7 @@ default_inputs:
                 nosym: False
                 occupations: smearing
                 smearing: cold
-                degauss: 0.01
+                degauss: 0.02
             ELECTRONS:
                 electron_maxstep: 80
                 mixing_beta: 0.4
@@ -43,13 +43,17 @@ protocols:
             parameters:
                 CONTROL:
                     forc_conv_thr: 0.5e-4
+                SYSTEM:
+                    degauss: 0.0125
     fast:
         description: 'Protocol to perform the computation at low precision at minimal computational cost for testing purposes.'
-        kpoints_distance: 0.50
+        kpoints_distance: 0.30
         meta_parameters:
             conv_thr_per_atom: 0.4e-9
             etot_conv_thr_per_atom: 1.e-4
         pw:
             parameters:
                 CONTROL:
                     forc_conv_thr: 1.e-3
+                SYSTEM:
+                    degauss: 0.0275