feat: Add timezone location support (#2705)

Closes #2688.

The PR adds support for timezone locations by embedding an [IANA
timezone database](https://github.com/eggert/tz) that gets loaded into
memory when gno.land is started. The gno stdlib's time package has been
updated by porting over code from the go stdlib to support locations.

This feature allows users to create time instances with locations to
ensure that temporal adjustments result in accurate results by following
both historical rules and current rules.

<details><summary>Contributors' checklist...</summary>

- [x] Added new tests, or not needed, or not feasible
- [x] Provided an example (e.g. screenshot) to aid review or the PR is
self-explanatory
- [x] Updated the official documentation or not needed
- [x] No breaking changes were made, or a `BREAKING CHANGE: xxx` message
was included in the description
- [x] Added references to related issues and PRs
- [x] Provided any useful hints for running manual tests
- [x] Added new benchmarks to [generated
graphs](https://gnoland.github.io/benchmarks), if any. More info
[here](https://github.com/gnolang/gno/blob/master/.benchmarks/README.md).
</details>

gnovm/stdlibs/time/timezoneinfo.gno

@@ -622,6 +622,8 @@ var errLocation = errors.New("time: invalid location name")
 
 var zoneinfo *string
 
+func loadFromEmbeddedTZData(name string) ([]byte, bool) // injected
+
 // XXX var zoneinfoOnce sync.Once
 
 // LoadLocation returns the Location with the given name.
@@ -640,41 +642,19 @@ var zoneinfo *string
 // - $GOROOT/lib/time/zoneinfo.zip
 // - the time/tzdata package, if it was imported
 func LoadLocation(name string) (*Location, error) {
-	panic("XXX LoadLocation not yet implemented")
-	/*
-		if name == "" || name == "UTC" {
-			return UTC, nil
-		}
-		if name == "Local" {
-			return Local, nil
-		}
-		if containsDotDot(name) || name[0] == '/' || name[0] == '\\' {
-			// No valid IANA Time Zone name contains a single dot,
-			// much less dot dot. Likewise, none begin with a slash.
-			return nil, errLocation
-		}
-		zoneinfoOnce.Do(func() {
-			env, _ := syscall.Getenv("ZONEINFO")
-			zoneinfo = &env
-		})
-		var firstErr error
-		if *zoneinfo != "" {
-			if zoneData, err := loadTzinfoFromDirOrZip(*zoneinfo, name); err == nil {
-				if z, err := LoadLocationFromTZData(name, zoneData); err == nil {
-					return z, nil
-				}
-				firstErr = err
-			} else if err != syscall.ENOENT {
-				firstErr = err
-			}
-		}
-		if z, err := loadLocation(name, platformZoneSources); err == nil {
-			return z, nil
-		} else if firstErr == nil {
-			firstErr = err
-		}
-		return nil, firstErr
-	*/
+	if name == "" || name == "UTC" {
+		return UTC, nil
+	}
+	if name == "Local" {
+		return Local, nil
+	}
+	if containsDotDot(name) || name[0] == '/' || name[0] == '\\' {
+		// No valid IANA Time Zone name contains a single dot,
+		// much less dot dot. Likewise, none begin with a slash.
+		return nil, errLocation
+	}
+
+	return loadLocation(name)
 }
 
 // containsDotDot reports whether s contains "..".

gnovm/stdlibs/time/tzdata.go

@@ -0,0 +1,74 @@
+package time
+
+// locationDefinitions are loaded during initialization using modified code from:
+// https://cs.opensource.google/go/go/+/refs/tags/go1.23.0:src/time/tzdata/tzdata.go
+var locationDefinitions = make(map[string][]byte)
+
+func init() {
+	const (
+		zecheader = 0x06054b50
+		zcheader  = 0x02014b50
+		ztailsize = 22
+
+		zheadersize = 30
+		zheader     = 0x04034b50
+	)
+
+	z := zipdata
+
+	idx := len(z) - ztailsize
+	n := get2s(z[idx+10:])
+	idx = get4s(z[idx+16:])
+
+	for i := 0; i < n; i++ {
+		// See time.loadTzinfoFromZip for zip entry layout.
+		if get4s(z[idx:]) != zcheader {
+			break
+		}
+		meth := get2s(z[idx+10:])
+		size := get4s(z[idx+24:])
+		namelen := get2s(z[idx+28:])
+		xlen := get2s(z[idx+30:])
+		fclen := get2s(z[idx+32:])
+		off := get4s(z[idx+42:])
+		zname := z[idx+46 : idx+46+namelen]
+		idx += 46 + namelen + xlen + fclen
+
+		if meth != 0 {
+			panic("unsupported compression for " + zname + " in embedded tzdata")
+		}
+
+		// See time.loadTzinfoFromZip for zip per-file header layout.
+		nidx := off
+		if get4s(z[nidx:]) != zheader ||
+			get2s(z[nidx+8:]) != meth ||
+			get2s(z[nidx+26:]) != namelen {
+			panic("corrupt embedded tzdata")
+		}
+
+		nxlen := get2s(z[nidx+28:])
+		nidx += 30 + namelen + nxlen
+		locationDefinitions[zname] = []byte(z[nidx : nidx+size])
+	}
+}
+
+// get4s returns the little-endian 32-bit value at the start of s.
+func get4s(s string) int {
+	if len(s) < 4 {
+		return 0
+	}
+	return int(s[0]) | int(s[1])<<8 | int(s[2])<<16 | int(s[3])<<24
+}
+
+// get2s returns the little-endian 16-bit value at the start of s.
+func get2s(s string) int {
+	if len(s) < 2 {
+		return 0
+	}
+	return int(s[0]) | int(s[1])<<8
+}
+
+func X_loadFromEmbeddedTZData(name string) ([]byte, bool) {
+	definition, ok := locationDefinitions[name]
+	return definition, ok
+}