feat(cabi): Add function to load SourceMapCache from disk

[loewenheim]

This also implements AsSelf for SourceMapCache and consequently removes the Inner and OwnedSourceMapCache types from CABI.

[codecov-commenter]

Codecov Report

Merging #691 (f50815c) into master (48c3195) will increase coverage by 0.01%. The diff coverage is 0.00%.

:exclamation: Current head f50815c differs from pull request most recent head ecbd97b. Consider uploading reports for the commit ecbd97b to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #691      +/-   ##
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+ Coverage   73.07%   73.08%   +0.01%     
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  Files          91       91              
  Lines       18313    18311       -2     
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+ Hits        13382    13383       +1     
+ Misses       4931     4928       -3     

[loewenheim]

lgtm, however symbolic_sourcemapcache_from_bytes is still constructing this completely in memory

Right, good point. Where do we want to save the cache? Do we create a temporary file?

[Swatinem]

I think you can just give it a path from the python side, python should have some named tempfile utilities.