This PR sets up the new integrated test/bench suite. It then migrates
all benchmarks and some related tests to the new suite. There's also
some documentation and some linting.
For now, a lot of the old tests are left alone so this PR doesn't become
even larger than it already is. Eventually, all tests should be migrated
to the new suite though so there isn't a confusing mix of two systems.
This PR provides an additional hint when the type of an autobound
implicit is required to have function type or equality type — this
fails, and the existing error message does not address the fact that the
source of the error is an unknown identifier that was automatically
bound.
## Example
```
import Lean
example : MetaM String := pure ""
```
Current error message:
```
Function expected at
MetaM
but this term has type
?m
Note: Expected a function because this term is being applied to the argument
String
```
Additional error message provided by this PR:
```
Hint: The identifier `MetaM` is unknown, and Lean's `autoImplicit` option
causes an unknown identifier to be treated as an implicitly bound variable
with an unknown type. However, the unknown type cannot be a function, and a
function is what Lean expects here. This is often the result of a typo or a
missing `import` or `open` statement.
```
