[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/filecache/compilationcache.go

@@ -0,0 +1,42 @@
+package filecache
+
+import (
+	"crypto/sha256"
+	"io"
+)
+
+// Cache allows the compiler engine to skip compilation of wasm to machine code
+// where doing so is redundant for the same wasm binary and version of wazero.
+//
+// This augments the default in-memory cache of compiled functions, by
+// decoupling it from a wazero.Runtime instance. Concretely, a runtime loses
+// its cache once closed. This cache allows the runtime to rebuild its
+// in-memory cache quicker, significantly reducing first-hit penalty on a hit.
+//
+// See New for the example implementation.
+type Cache interface {
+	// Get is called when the runtime is trying to get the cached compiled functions.
+	// Implementations are supposed to return compiled function in io.Reader with ok=true
+	// if the key exists on the cache. In the case of not-found, this should return
+	// ok=false with err=nil. content.Close() is automatically called by
+	// the caller of this Get.
+	//
+	// Note: the returned content won't go through the validation pass of Wasm binary
+	// which is applied when the binary is compiled from scratch without cache hit.
+	Get(key Key) (content io.ReadCloser, ok bool, err error)
+	//
+	// Add is called when the runtime is trying to add the new cache entry.
+	// The given `content` must be un-modified, and returned as-is in Get method.
+	//
+	// Note: the `content` is ensured to be safe through the validation phase applied on the Wasm binary.
+	Add(key Key, content io.Reader) (err error)
+	//
+	// Delete is called when the cache on the `key` returned by Get is no longer usable, and
+	// must be purged. Specifically, this is called happens when the wazero's version has been changed.
+	// For example, that is when there's a difference between the version of compiling wazero and the
+	// version of the currently used wazero.
+	Delete(key Key) (err error)
+}
+
+// Key represents the 256-bit unique identifier assigned to each cache entry.
+type Key = [sha256.Size]byte