Also add validate-8.10.1 make rule

Mark public libs as an experimental feature

Split D.Client.Types module

Add forEachGPD to hackage-tests

Allow specify index-state per repository

This allows to quickly write ad-hoc queries over Hackage
data.

Move IndexState to own module

Parser benchmark

The speed-up is smaller than I would like, only 1-2%.

Add Described FlagName and RepoName instances

Move few Arbitrary instances to more correct places,
add tests

Installing (copy or symlink) executable message prints destination.

Add Described to IndexState (incl. tests).

- Writing a regex to parse dates is awful.
- Add ShortText conversions to PackageName and UnqualComponentName
- Add mkDependency, which maintains the invariant
- Remove VersionRangeParens - it's not preserved by parsec . pretty
  roundtrip
- Move moree instances into Cabal-quickcheck,
  use the package in cabal-install tests

More checks in version range parser

Do this already in the Parsec instance parser.
This allows removing checks from `D.PD.Check`.
Later this would also allow removing non-relevant
constructors from `VersionRange`, allowing easier testing.

This change causes 10% slowdown: from

```
135768 files processed
  7350 files contained warnings
113156 files have check warnings
     0 files failed to parse

120.901201s elapsed
117.640431s elapsed
119.663620s elapsed
119.454329s elapsed
119.785214s elapsed
```

to

```
135768 files processed
 31912 files contained warnings
113109 files have check warnings
     0 files failed to parse

130.969593s elapsed
132.016403s elapsed
134.214536s elapsed
128.753382s elapsed
131.503804s elapsed
```

I hope the slowdown is acceptable, and I have an idea which may mitigate
this. I'll try out it after I done further refactorings.

Note how (parser) warnings grew by a factor. There are plenty of (old)
files on Hackage, which don't use correct cabal-version.  For that
reason we only issue warnings, and not fail.  Quirks approach won't
scale for these. In comparison, there are even more files
with check warnings

- remove parallel code, it's complicated and doesn't speedup reliably
- count files with warning
- add --keep-going
- add `clock` measurement from inside the parsec test

Add Quirk for single invalid UTF8 file.

Partially fixes https://github.com/haskell/cabal/issues/6587
For local files, there might be invalid UTF8; but if
file comes from Hackage, we can assume they are valid UTF8.

Remove MONOLITHIC build

Add RepoName newtype

Make it, LocalRepo, RemoteRepo, IndexState and Timestamp use
Pretty/Parsec instead of Text

Mostly adding `unRepoName` to error printing statements

Resolve #6369 and #6393: Allow cabal v2-install pkgname:exename or http://example.com/package.tar.gz(#sha256=abcde...)

We can write URIs with a fragment like

    https://hackage.haskell.org/package/cabal-fmt-0.1.2/cabal-fmt-0.1.2.tar.gz#sha256=aae556efbcaddfd65c6a1c1811b122b0d8c8d00624c8c2e36aabb5e9f9ea9840

and downloadURI will check the hash after download before continuing.
The hash check supersedes ETag