[performance] media processing improvements

[NyaaaWhatsUpDoc]

Description

• pulls in latest go-store and go-cache versions
• wraps media encoding/decoding handling to be mostly contained within gtsImage{} and gtsVideo{} types for neatness
• decreases JPEG thumb quality to 70% (it's only a thumb, helps with filesize)
• uses memory pools for JPEG and PNG encoding
• updates media processing to no longer use the atomic state variables (as these were mostly unused), all is now just done within mutex
• general tidy-up of media processing which improves: neatness, memory usage, error handling
• use larger write buffer size when streaming data into storage (now uses 16KiB, previously used 4KiB which is quite small)
• fix presigned S3 URL cache call (fixes [bug] Panic probably related to S3 presigned URL caching #1279)
• changes test filenames / paths to fit with updated changes
• removes tee'd streaming of recache to both client and storage: in cases of slow client connections each tee stream could block a media worker pool function, which on instances with multiple users could very quickly exhaust available media workers
• run a disk storage clean operation (removes empty folders) on storage open

Checklist

• I/we have read the GoToSocial contribution guidelines.
• I/we have discussed the proposed changes already, either in an issue on the repository, or in the Matrix chat.
• I/we have performed a self-review of added code.
• I/we have written code that is legible and maintainable by others.
• I/we have commented the added code, particularly in hard-to-understand areas.
• I/we have made any necessary changes to documentation.
• I/we have added tests that cover new code.
• I/we have run tests and they pass locally with the changes.
• I/we have run go fmt ./... and golangci-lint run.

[tsmethurst]

Still reviewing but it looks good so far. Does it make sense to try to include #1295 in this, or should that be a separate PR? Either is OK imo

[NyaaaWhatsUpDoc]

Still reviewing but it looks good so far. Does it make sense to try to include #1295 in this, or should that be a separate PR? Either is OK imo

it might as well be included in this PR tbh :)

[tsmethurst]

Looks fucking great in general. I have a few small comments, but this seems more or less ready to merge, to me. Thanks for your hard work on this!! <3