[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/cache/visibility.go

@@ -18,18 +18,16 @@
 package cache
 
 import (
-	"codeberg.org/gruf/go-cache/v3/result"
+	"codeberg.org/gruf/go-structr"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
 )
 
 type VisibilityCache struct {
-	*result.Cache[*CachedVisibility]
+	structr.Cache[*CachedVisibility]
 }
 
-// Init will initialize the visibility cache in this collection.
-// NOTE: the cache MUST NOT be in use anywhere, this is not thread-safe.
-func (c *VisibilityCache) Init() {
+func (c *Caches) initVisibility() {
 	// Calculate maximum cache size.
 	cap := calculateResultCacheMax(
 		sizeofVisibility(), // model in-mem size.
@@ -38,25 +36,22 @@ func (c *VisibilityCache) Init() {
 
 	log.Infof(nil, "Visibility cache size = %d", cap)
 
-	c.Cache = result.New([]result.Lookup{
-		{Name: "ItemID", Multi: true},
-		{Name: "RequesterID", Multi: true},
-		{Name: "Type.RequesterID.ItemID"},
-	}, func(v1 *CachedVisibility) *CachedVisibility {
+	copyF := func(v1 *CachedVisibility) *CachedVisibility {
 		v2 := new(CachedVisibility)
 		*v2 = *v1
 		return v2
-	}, cap)
+	}
 
-	c.Cache.IgnoreErrors(ignoreErrors)
-}
-
-// Start will attempt to start the visibility cache, or panic.
-func (c *VisibilityCache) Start() {
-}
-
-// Stop will attempt to stop the visibility cache, or panic.
-func (c *VisibilityCache) Stop() {
+	c.Visibility.Init(structr.Config[*CachedVisibility]{
+		Indices: []structr.IndexConfig{
+			{Fields: "ItemID", Multiple: true},
+			{Fields: "RequesterID", Multiple: true},
+			{Fields: "Type,RequesterID,ItemID"},
+		},
+		MaxSize:   cap,
+		IgnoreErr: ignoreErrors,
+		CopyValue: copyF,
+	})
 }
 
 // VisibilityType represents a visibility lookup type.