Merge getBH_dict into getBH

[Alexboiboi]

This PR aims to merge the functionality of the getB_dict and getH_dict into getB and getH respectively, in order to make the top level interface less cluttered. This introduces some minor breaking changes by removing getB_dict and getH_dict functions from the library top level. These library can still be accessed privately, as they remain unchanged internally.
The original getB and getH function remain unchanged in their classical use.

Before

import magpylib as magpy
import numpy as np

B = magpy.getB_dict(
    source_type = 'Cuboid',
    observer = (1,2,3),
    magnetization = np.linspace((0.,0.,500.),(0.,0.,1000.),6),
    dimension = np.linspace((1.,1.,1.),(2.,2.,2.),6)
)
print(B)

After

import magpylib as magpy
import numpy as np

B = magpy.getB(
    'Cuboid',
    (1,2,3),
    magnetization = np.linspace((0.,0.,500.),(0.,0.,1000.),6),
    dimension = np.linspace((1.,1.,1.),(2.,2.,2.),6)
)
print(B)

Note

providing kwargs when the source is not a string will raise an error

import magpylib as magpy
import numpy as np

cuboid  = magpy.magnet.Cuboid((0,0,1), (1,1,1))

B = magpy.getB(
    cuboid,
    (1,2,3),
    magnetization = np.linspace((0.,0.,500.),(0.,0.,1000.),6),
    dimension = np.linspace((1.,1.,1.),(2.,2.,2.),6)
)
## raises MagpylibBadUserInput

TODO

• modify getB and getH
• update tests
• update docstrings
• update changelog
• update documentation

[codecov-commenter]

Codecov Report

Merging #449 (acc80a2) into development (3da5b03) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           development     #449   +/-   ##
============================================
  Coverage        99.75%   99.75%           
============================================
  Files               49       49           
  Lines             4883     4888    +5     
============================================
+ Hits              4871     4876    +5     
  Misses              12       12           

Impacted Files	Coverage Δ
magpylib/__init__.py	100.00% <100.00%> (ø)
magpylib/_src/fields/field_wrap_BH_level2.py	100.00% <100.00%> (ø)
magpylib/_src/fields/field_wrap_BH_level3.py	100.00% <100.00%> (ø)

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