perf(gnovm): cache PkgIDFromPkgPath for higher performance

This change comes from noticing that PkgIDFromPkgPath is very
heavily invoked within the VM yet its results with the same inputs
produced deterministic results aka SHA256(path)[:20]
Previously just spinning up the VM would take 80 seconds, with this
change that's shaved by ~8-10 seconds down and with repeatable and
visible results exhibited through profiles:

* Before
```shell
(pprof) list PkgIDFromPkgPath
Total: 100.94s
ROUTINE ======================== github.com/gnolang/gno/gnovm/pkg/gnolang.PkgIDFromPkgPath in $PATH
     220ms      9.26s (flat, cum)  9.17% of Total
         .          .     74:func PkgIDFromPkgPath(path string) PkgID {
     220ms      9.26s     75:	return PkgID{HashBytes([]byte(path))}
         .          .     76:}
         .          .     77:
         .          .     78:// Returns the ObjectID of the PackageValue associated with path.
         .          .     79:func ObjectIDFromPkgPath(path string) ObjectID {
         .          .     80:	pkgID := PkgIDFromPkgPath(path)
```

* After
```shell
(pprof) list PkgIDFromPkgPath
Total: 93.22s
ROUTINE ======================== github.com/gnolang/gno/gnovm/pkg/gnolang.PkgIDFromPkgPath in $PATH
     210ms      1.55s (flat, cum)  1.66% of Total
      50ms       50ms     78:func PkgIDFromPkgPath(path string) PkgID {
         .      490ms     79:	pkgIDMu.Lock()
      10ms       10ms     80:	defer pkgIDMu.Unlock()
         .          .     81:
      10ms      730ms     82:	pkgID, ok := pkgIDFromPkgPathCache[path]
         .          .     83:	if !ok {
         .          .     84:		pkgID = new(PkgID)
         .          .     85:		*pkgID = PkgID{HashBytes([]byte(path))}
         .          .     86:		pkgIDFromPkgPathCache[path] = pkgID
         .          .     87:	}
     140ms      270ms     88:	return *pkgID
         .          .     89:}
         .          .     90:
         .          .     91:// Returns the ObjectID of the PackageValue associated with path.
         .          .     92:func ObjectIDFromPkgPath(path string) ObjectID {
         .          .     93:	pkgID := PkgIDFromPkgPath(path)
```

Fixes #3423

gnovm/pkg/gnolang/realm.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"reflect"
 	"strings"
+	"sync"
 
 	bm "github.com/gnolang/gno/gnovm/pkg/benchops"
 )
@@ -71,8 +72,20 @@ func (pid PkgID) Bytes() []byte {
 	return pid.Hashlet[:]
 }
 
+var pkgIDMu sync.Mutex // pkgIDMu protects the shared cache.
+var pkgIDFromPkgPathCache = make(map[string]*PkgID)
+
 func PkgIDFromPkgPath(path string) PkgID {
-	return PkgID{HashBytes([]byte(path))}
+	pkgIDMu.Lock()
+	defer pkgIDMu.Unlock()
+
+	pkgID, ok := pkgIDFromPkgPathCache[path]
+	if !ok {
+		pkgID = new(PkgID)
+		*pkgID = PkgID{HashBytes([]byte(path))}
+		pkgIDFromPkgPathCache[path] = pkgID
+	}
+	return *pkgID
 }
 
 // Returns the ObjectID of the PackageValue associated with path.