Avoid included bib circular inclusion, de-duplicate included tex, cache getter tests

.gitignore

src/core/cache.ts

.../fixtures/unittest/03_core_cache/included_bib/another.tex

...xtures/unittest/03_core_cache/included_bib/circular_1.tex

...xtures/unittest/03_core_cache/included_bib/circular_2.tex

...tures/unittest/03_core_cache/included_bib/duplicate_1.tex

...tures/unittest/03_core_cache/included_bib/duplicate_2.tex

test/fixtures/unittest/03_core_cache/included_bib/main.bib

test/fixtures/unittest/03_core_cache/included_bib/main.tex

.../fixtures/unittest/03_core_cache/included_tex/another.tex

...xtures/unittest/03_core_cache/included_tex/circular_1.tex

...xtures/unittest/03_core_cache/included_tex/circular_2.tex

...tures/unittest/03_core_cache/included_tex/duplicate_1.tex

...tures/unittest/03_core_cache/included_tex/duplicate_2.tex

test/fixtures/unittest/03_core_cache/included_tex/main.tex

test/fixtures/unittest/03_core_cache/load_aux_file/main.aux

test/fixtures/unittest/03_core_cache/load_aux_file/main.bib

test/fixtures/unittest/03_core_cache/load_aux_file/main.fls

test/fixtures/unittest/03_core_cache/load_aux_file/main.tex

...fixtures/unittest/03_core_cache/load_aux_file/nothing.aux