add support for alternate easyconfig parameters/templates/constants

[jfgrimm]

As discussed in slack, this is an alternative approach to introducing new parameters and deprecating old ones in one go. Instead, it's a multi-stage process:

1. Introduce new names, as alternatives
2. Do the renaming
3. Deprecate
   This would allow is to do it iteratively across the different parameters / etc. over a series of EB 5.x releases.

#4464

To play around with this, check out the branch and modify:

• easybuild/framework/easyconfig/parser.py:

 45 # alternate easyconfig parameters, and their non-deprecated equivalents                                                 
 46 ALTERNATE_PARAMETERS = {                                                                                                
 47     # <new_param>: <equivalent_param>,                                                                                  
 48 } 

• easybuild/framework/easyconfig/templates.py:

164 # alternate templates, and their equivalents                                                                            
165 ALTERNATE_TEMPLATES = {                                                                                                 
166     # <new>: <equivalent_template>,                                                                                     
167 }

174 # alternate template constants, and their equivalents                                                                   
175 ALTERNATE_TEMPLATE_CONSTANTS = {                                                                                        
176     # <new_template_constant>: <equivalent_template_constant>,                                                          
177 }

[jfgrimm]

not really sure what I've done wrong, it works when you run the test in isolation...

FAIL: test_template_deprecation_and_alternate (test.framework.easyconfig.EasyConfigTest.test_template_deprecation_and_alternate)
Test deprecation of (and alternate) templates
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/runner/8eb0620a58092b2b260f5fc629e7607eac6df691/lib/python3.11/site-packages/test/framework/easyconfig.py", line 1498, in test_template_deprecation_and_alternate
    self.assertNotIn("%(" + tmpl + ")s", res)
AssertionError: '%(builddir)s' unexpectedly found in "cd %(start_dir)s && make %(namelower)s -Dbuild=%(builddir)s --with-cuda='%(cudaver)s' && echo %(alt_install_dir)s %(version_major_minor)s"