OSLog is the suggesting logging solution on Apple platforms and we should be using it there, taking advantage of the different log levels and privacy masking.
Switch sourcekit-lsp to use OSLog on Apple platforms and implement a logger that is API-compatible with OSLog for all uses in sourcekit-lsp and which can be used on non-Darwin platforms.
The goal of this commit is to introduce the new logging API. There are still improvements about what we log and we can display more privacy-insensitive information after masking. Those changes will be in follow-up commits.
Add `.swift-format` to the repo and format the repo with `swift-format`.
This commit does not add any automation to enforce formatting of sourcekit-lsp in CI. The goal of this commit is to get the majority of source changes out of the way so that the diff of actually enforcing formatting will have fewer changes or conflicts.
