feat(redis): opt-in `raw` support

[cjpearson]

Resolves #559

This change adds a new saveRawAsBinary option to the redis driver. When enabled, the driver will use the setBuffer and getBuffer methods of ioredis to directly save Buffers rather than base64 encoding and saving as a string. The option is not enabled by default as that would be a backwards incompatible change.

When #528 is implemented, this could be made the default for {type: 'bytes'}. (Perhaps then saveBytesAsBinary is a better name?) It would also be possible to drop the base64 encoding entirely and instead allow users to manually encode and save as { type: 'text' }.

[codecov[bot]]

Codecov Report

:x: Patch coverage is 64.15094% with 19 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 60.07%. Comparing base (4d61c78) to head (b92591e). :warning: Report is 225 commits behind head on main.

Files with missing lines	Patch %	Lines
src/drivers/redis.ts	64.15%	11 Missing and 8 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #561      +/-   ##
==========================================
- Coverage   65.05%   60.07%   -4.98%     
==========================================
  Files          39       42       +3     
  Lines        4055     3702     -353     
  Branches      487      615     +128     
==========================================
- Hits         2638     2224     -414     
- Misses       1408     1467      +59     
- Partials        9       11       +2     

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