Rollup merge of #153491 - ChrisDenton:openoptionsext2, r=Mark-Simulacrum

Move `freeze_*` methods to `OpenOptionsExt2`

Move the unstable `freeze_last_access_time` and `freeze_last_write_time` from `OpenOptionsExt` to a new `OpenOptionsExt2` trait. This should fix rust-lang/rust#153486.

Author: JonathanBrouwer