Introduce CursorState to consolidate per-cursor memory tracking · awslabs/mountpoint-s3@29a8de9

Run tests: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L1002

struct `fuse_notify_retrieve_in` is never constructed

Run tests: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L992

struct `fuse_notify_retrieve_out` is never constructed

Run tests: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L864

struct `fuse_ioctl_iovec` is never constructed

Run tests: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L819

struct `cuse_init_out` is never constructed

Run tests: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L810

struct `cuse_init_in` is never constructed

Validate ASan is working: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L1002

struct `fuse_notify_retrieve_in` is never constructed

Validate ASan is working: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L992

struct `fuse_notify_retrieve_out` is never constructed

Validate ASan is working: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L864

struct `fuse_ioctl_iovec` is never constructed

Validate ASan is working: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L819

struct `cuse_init_out` is never constructed

Validate ASan is working: mountpoint-s3-fuser/src/ll/fuse_abi.rs#L810

struct `cuse_init_in` is never constructed

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