Why:
* To implement robust cross-project go-to-definition in LSP
i.e you can jump to definition of any global name coming
from library dependencies, as well as from the local project files.
What it does:
* Modify `FC`s to carry `ModuleIdent` for .idr sources,
file name for .ipkg sources or nothing for interactive runs.
* Add `--install-with-src` to install the source code alongside
the ttc binaries. The source is installed into the same directory
as the corresponding ttc file. Installed sources are made read-only.
* As we install the sources pinned to the related ttc files we gain
the versioning of sources for free.
Where 'small' means they don't refer to other metavariables, except
right at the top level, and they don't go beyond a certain small depth,
arrived at by experimenting.
We already did a bit of this, but only for depth 0. The effect of this
is that we don't need to save out lots of metavariables, so ttc loading
is faster. This takes about 8s off the Idris build time!
All of these internal names are making the output fragile. This
cleanup should allow us to only have to update the golden file
when there is a genuinely interesting change.
