Add a helper method to enable/disable plugins during staging of Eiger detectors

[mrakitin]

During today's CHX visit with @oksanagit, @jklynch, @AbbyGi, @MikeHart85 over zoom and Lutz in person, we tried this method to disable plugins during the staging process of the eiger1m_single detector to speed up the acquisition process:

for i in range(1, 4+1):
    getattr(eiger1m_single, f'roi{i}').stage_sigs = OrderedDict([('enable', 0),
             ('blocking_callbacks', 'No'),
             ('parent.cam.array_callbacks', 1)])

for i in range(1, 5+1):
    getattr(eiger1m_single, f'stats{i}').stage_sigs = OrderedDict([('enable', 0),
             ('blocking_callbacks', 'No'),
             ('parent.cam.array_callbacks', 1)])

eiger1m_single.proc1.stage_sigs = OrderedDict([('enable', 0),
             ('blocking_callbacks', 'No'),
             ('parent.cam.array_callbacks', 1)])

eiger1m_single.image.stage_sigs = OrderedDict([('enable', 0),
             ('blocking_callbacks', 'No'),
             ('parent.cam.array_callbacks', 1)])

We also figured out the non-blocking plugin mode was only enabled for eiger4m_single, but not for the other 2 detectors (eiger500k_single and eiger1m_single). de6e031 resolved it. We did a few tests with manipulation of the ['roi1', 'roi2', 'roi3', 'roi4', 'stats1', 'stats2', 'stats3', 'stats4', 'stats5', 'proc1', 'image'] plugins, and the results are as follows:

• all plugins enabled/blocking mode: 2000 frames with 0.001 s/frame took ~20s;
• all plugins enabled/non-blocking mode: 2000 frames with 0.001 s/frame took ~9s on the first run after bsui restart, and ~6.8s for the subsequent runs;
• all plugins disabled/non-blocking mode: 2000 frames with 0.001 s/frame took ~9s on the first run after bsui restart, and ~6.8s for the subsequent runs.

The last 2 cases were comparable in terms of the speed of the scan, but when all plugins are enabled/non-blocking, the resource use is significantly higher than when the plugins are disabled. So, the current PR's update is to provide a way to disable the plugins when needed (they are enabled by default).

Usage:

eiger1m_single.enable_plugins()  # to enable the plugins
eiger1m_single.enable_plugins(enable=False)  # to disable the plugins

This needs to be tested thoroughly before going to production, preferably with the beam.