ENH: extend message for a NoDatasetArgumentFound in require_dataset

[yarikoptic]

This exception is now (since 0.12) is frequently shown to users due to breakage
of behavior as discussed in #3759 .
As it is worded minimally, it provides no instructions to the users and just
brings frustration. This commit extends message to provide instructions on how
to mitigate the error they start to observe

[codecov]

Codecov Report

Merging #4285 into maint will decrease coverage by 0.05%.
The diff coverage is 96.42%.

@@            Coverage Diff             @@
##            maint    #4285      +/-   ##
==========================================
- Coverage   89.66%   89.61%   -0.06%     
==========================================
  Files         275      275              
  Lines       36857    36864       +7     
==========================================
- Hits        33048    33035      -13     
- Misses       3809     3829      +20     

Impacted Files	Coverage Δ
datalad/metadata/search.py	83.37% <80.00%> (ø)
datalad/core/local/tests/test_diff.py	99.48% <100.00%> (ø)
datalad/core/local/tests/test_run.py	98.68% <100.00%> (ø)
datalad/core/local/tests/test_status.py	98.86% <100.00%> (ø)
datalad/distribution/dataset.py	95.86% <100.00%> (ø)
datalad/interface/download_url.py	97.89% <100.00%> (ø)
datalad/interface/run_procedure.py	90.68% <100.00%> (ø)
datalad/interface/tests/test_unlock.py	98.09% <100.00%> (ø)
datalad/metadata/tests/test_base.py	99.30% <100.00%> (ø)
datalad/metadata/tests/test_search.py	94.96% <100.00%> (ø)
... and 7 more

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[mih]

Pushed to additionsto the original change. Cummulative effect is:

/tmp % datalad status
[ERROR  ] No dataset found at '/tmp'.  Specify a dataset to work with by providing its path via the `dataset` option, or change the current working directory to be in a dataset. [dataset.py:require_dataset:570] (NoDatasetFound)