enhancement/fix/change: re-organization/normalization of builtin back-ends with switch of new file based test data for them

[ssato]

change:

• normalize the IDs of the builtin parsers to allow addition of different back-end (loader/dumper) for each format easier
• re-organization of the builtin parseres to accomplish the above
• replace code based test cases with test cases and file based test data

enhancements:

• add new and more exhaustive file based test data for the builtin parsers to allow addition of test cases for loaders and dumpers inside the parers at lower cost

fixes:

• void extra \r to be added to each output lines in ini dumper: ini (ini.configparser), properties (properties.builtin), sh (sh.variables)
• correction of some lint and type hints errors

[codecov[bot]]

Codecov Report

Attention: 10 lines in your changes are missing coverage. Please review.

Comparison is base (be327b0) 95.11% compared to head (838f5b0) 95.87%. Report is 8 commits behind head on next.

Files	Patch %	Lines
tests/common/load.py	85.00%	3 Missing :warning:
tests/common/dumper.py	93.54%	2 Missing :warning:
tests/common/loader.py	91.66%	2 Missing :warning:
tests/backend/dumpers/toml/test_toml_tomllib.py	95.45%	1 Missing :warning:
tests/backend/loaders/toml/test_toml_tomllib.py	95.65%	1 Missing :warning:
tests/common/load_py.py	96.66%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## next #159 +/- ## ========================================== + Coverage 95.11% 95.87% +0.75% ========================================== Files 203 271 +68 Lines 4504 4630 +126 ========================================== + Hits 4284 4439 +155 + Misses 220 191 -29 ```

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