[performance] overhaul struct (+ result) caching library for simplicity, performance and multiple-result lookups (#2535)

* rewrite cache library as codeberg.org/gruf/go-structr, implement in gotosocial

* use actual go-structr release version (not just commit hash)

* revert go toolchain changes (damn you go for auto changing this)

* fix go mod woes

* ensure %w is used in calls to errs.Appendf()

* fix error checking

* fix possible panic

* remove unnecessary start/stop functions, move to main Cache{} struct, add note regarding which caches require start/stop

* fix copy-paste artifact... 😇

* fix all comment copy-paste artifacts

* remove dropID() function, now we can just use slices.DeleteFunc()

* use util.Deduplicate() instead of collate(), move collate to util

* move orderByIDs() to util package and "generify"

* add a util.DeleteIf() function, use this to delete entries on failed population

* use slices.DeleteFunc() instead of util.DeleteIf() (i had the logic mixed up in my head somehow lol)

* add note about how collate differs from deduplicate

internal/processing/status/create.go

@@ -229,6 +229,7 @@ func (p *Processor) processMediaIDs(ctx context.Context, form *apimodel.Advanced
 
 	attachments := []*gtsmodel.MediaAttachment{}
 	attachmentIDs := []string{}
+
 	for _, mediaID := range form.MediaIDs {
 		attachment, err := p.state.DB.GetAttachmentByID(ctx, mediaID)
 		if err != nil && !errors.Is(err, db.ErrNoEntries) {