[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

vendor/github.com/tetratelabs/wazero/internal/wasm/binary/value.go

@@ -0,0 +1,60 @@
+package binary
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"unicode/utf8"
+	"unsafe"
+
+	"github.com/tetratelabs/wazero/internal/leb128"
+	"github.com/tetratelabs/wazero/internal/wasm"
+)
+
+func decodeValueTypes(r *bytes.Reader, num uint32) ([]wasm.ValueType, error) {
+	if num == 0 {
+		return nil, nil
+	}
+
+	ret := make([]wasm.ValueType, num)
+	_, err := io.ReadFull(r, ret)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, v := range ret {
+		switch v {
+		case wasm.ValueTypeI32, wasm.ValueTypeF32, wasm.ValueTypeI64, wasm.ValueTypeF64,
+			wasm.ValueTypeExternref, wasm.ValueTypeFuncref, wasm.ValueTypeV128:
+		default:
+			return nil, fmt.Errorf("invalid value type: %d", v)
+		}
+	}
+	return ret, nil
+}
+
+// decodeUTF8 decodes a size prefixed string from the reader, returning it and the count of bytes read.
+// contextFormat and contextArgs apply an error format when present
+func decodeUTF8(r *bytes.Reader, contextFormat string, contextArgs ...interface{}) (string, uint32, error) {
+	size, sizeOfSize, err := leb128.DecodeUint32(r)
+	if err != nil {
+		return "", 0, fmt.Errorf("failed to read %s size: %w", fmt.Sprintf(contextFormat, contextArgs...), err)
+	}
+
+	if size == 0 {
+		return "", uint32(sizeOfSize), nil
+	}
+
+	buf := make([]byte, size)
+	if _, err = io.ReadFull(r, buf); err != nil {
+		return "", 0, fmt.Errorf("failed to read %s: %w", fmt.Sprintf(contextFormat, contextArgs...), err)
+	}
+
+	if !utf8.Valid(buf) {
+		return "", 0, fmt.Errorf("%s is not valid UTF-8", fmt.Sprintf(contextFormat, contextArgs...))
+	}
+
+	// TODO: use unsafe.String after flooring Go 1.20.
+	ret := *(*string)(unsafe.Pointer(&buf))
+	return ret, size + uint32(sizeOfSize), nil
+}