Add case-insensitive name clash test

[branfosj]

See #11824

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FAIL: test_easyconfig_name_clashes (test.easyconfigs.easyconfigs.EasyConfigTest)
Make sure there is not a name clash when all names are lowercase
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Traceback (most recent call last):
  File "/home/runner/work/easybuild-easyconfigs/easybuild-easyconfigs/test/easyconfigs/easyconfigs.py", line 953, in test_easyconfig_name_clashes
    self.assertTrue(False, "EasyConfigs with case-insensitive name clash: %s" % duplicates)
AssertionError: False is not true : EasyConfigs with case-insensitive name clash: {'arb': ['ARB', 'Arb'], 'nanofilt': ['NanoFilt', 'nanofilt'], 'ncl': ['NCL', 'ncl'], 'check': ['Check', 'check'], 'charmm': ['charmm', 'CHARMM'], 'graphviz': ['Graphviz', 'graphviz'], 'magma': ['MAGMA', 'magma'], 'libpsml': ['libpsml', 'libPSML'], 'bamm': ['BAMM', 'BamM'], 'blasr': ['BLASR', 'blasr']}

[lexming]

LGTM

[lexming]

Going in, thanks @branfosj !