Add cel::Value::WrapMessageUnsafe.

Adds an unsafe version of wrap message that avoids copies but risks less obvious lifetime dependencies.

PiperOrigin-RevId: 833378293

Bump abseil and protobuf versions.

Use the `absl_nullable` style of nullability annotations.

PiperOrigin-RevId: 788564038

Suppress clang warning for direct memory write in value_variant.h.

PiperOrigin-RevId: 781114095

Update to cel-spec 0.23.0

PiperOrigin-RevId: 743693479

Move `CheckerOptions` to the `cel` namespace

PiperOrigin-RevId: 689503156

Update the default type provider (protobuf reflection impl) to return…

… a specific

type info instance instead of the generic one.

PiperOrigin-RevId: 534552333

Merge pull request #155 from google/cpp-sync

Internal change

Merge pull request #133 from google/cpp-sync

OSS export

Merge pull request #124 from google/oss_fixes

strings: fix invalid access with UTF8 verification, ensure absl::string_view compatibility

Merge pull request #123 from google/cpp-sync

OSS Export