Implement new Enso documentation parser; remove old Scala Enso parser.
Performance: Total time parsing documentation is now ~2ms.
# Important Notes
- Doc parsing is now done only in the frontend.
- Some engine tests had never been switched to the new parser. We should investigate tests that don't pass after the switch: #5894.
- The option to run the old searcher has been removed, as it is obsolete and was already broken before this (see #5909).
- Some interfaces used only by the old searcher have been removed.
- Added expression ANTLR4 grammar and sbt based build.
- Added expression support to `set` and `filter` on the Database and InMemory `Table`.
- Added expression support to `aggregate` on the Database and InMemory `Table`.
- Removed old aggregate functions (`sum`, `max`, `min` and `mean`) from `Column` types.
- Adjusted database `Column` `+` operator to do concatenation (`||`) when text types.
- Added power operator `^` to both `Column` types.
- Adjust `iif` to allow for columns to be passed for `when_true` and `when_false` parameters.
- Added `is_present` to database `Column` type.
- Added `coalesce`, `min` and `max` functions to both `Column` types performing row based operation.
- Added support for `Date`, `Time_Of_Day` and `Date_Time` constants in database.
- Added `read` method to InMemory `Column` returning `self` (or a slice).
# Important Notes
- Moved approximate type computation to `SQL_Type`.
- Fixed issue in `LongNumericOp` where it was always casting to a double.
- Removed `head` from InMemory Table (still has `first` method).
Result of automatic formatting with `scalafmtAll` and `javafmtAll`.
Prerequisite for https://github.com/enso-org/enso/pull/3394
### Important Notes
This touches a lot of files and might conflict with existing PRs that are in progress. If that's the case, just run
`scalafmtAll` and `javafmtAll` after merge and everything should be in order since formatters should be deterministic.
File Manager — an Akka-based service providing a basic filesystem-like API over network. Currently it just wraps the local filesystem operations. In the future support for other kinds of storage might get added. Ref #32
