acq drift: correctly handle too small resolution

also warn if such case happen
gui/acq: improve drift correction setting and MDStream

now explicitely create MDStream, so no need to have hack in the acq manager to merge streams

Rename DRIFTCOR tool to more explicit RO_ANCHOR.

Add logic to keep the dcRegion to the minimum size in the SEM stream

Add logic to update the dcDwellTime according to the SEM survey

Ensure the whole GUI selection of the Anchor region works fine in general.
acq: prefer fluo stream with long emission wl first

According to one source that Lennard heard, it's better... At least he never heard anyone claiming the opposite, so it might be better than random.
acq: move check for UNDEFINED_ROI outside of AnchoredEstimator

Assume that the estimator always receives a good ROI, and it's up to the caller to ensure that the ROI is not
the special UNDEFINED_ROI.

As a side effect, it nicely avoids a double definition of UNDEFINED_ROI
acq drift: make estimateCorrectionPeriod a static method

It doesn't need the estimator to compute the result, so make it static.

Actually, it should be identical for any kind of drift estimator, so we probably should make it a
function of the drift module, instead of the estimator to be perfectly logical.
acq test: fix tests for SPARC

now the acq manager expect the MD streams to already be created.
driver detectors: fix handling of deref of weakref

the change from a proxy to a normal wearef also changes the way the deref is detected.
acq: refactor so that we only have one executeTask

move all the futures-related code to a separate module

remove duplicate versions of executeTask.

Still need to be done on find_overlay when the latest version is merged.