New documents to checkpoint my work on #329 and #87

See merge request tpo/core/arti!407

tor-netdoc: use InternCache to save memory for families and protover lists

Closes #384 and #385

See merge request tpo/core/arti!398

# Conflicts:
#   doc/semver_status.md

These documents explain how to profile arti for CPU and memory, and
how to simulate different kinds of breakage and misconfiguration.

They aren't at all in their final form, but I figure it's useful to
check them in so that more people can look at them, and make
suggestions.

dirmgr: Call shrink_to_fit on missing-microdesc hashtable

Closes #388

See merge request tpo/core/arti!399

Simpify tor-netdoc TokVal

See merge request tpo/core/arti!404

Replace humantime_serde_option with upstream code

Closes #396

See merge request tpo/core/arti!406

We have upstreamed this code.

This reverts commit 6193c9d9.

Replace all uses of our copy of this code.

This has the humantime_serde::option module, which we have upstreamed
and are about to switch to.

The remaining dependency with  version = "1"  is going to be removed
in a moment.

This should save around 1MB per consensus, since every relay has a
'protocols' lines, but there are only a few distinct possibilities
for such a line.

Closes #385.

This should save 1-3 MB of ram on each running arti client.

Closes #384. See also tor#27359 and proposal 298.

arti: Move all code from binary crate to library crate

See merge request tpo/core/arti!403

tor-netdoc: Save allocation space in GenericRouterstatus

Closes #387

See merge request tpo/core/arti!400

(Once we're done parsing these, the vector will never get any
longer.)

This should save around 181K of heap on a current directory.

When the version is a Tor version, we can just parse it; otherwise,
we can intern it.  This shrinks GenericRouterStatus and avoids a lot
of extra help allocations.

This is the default vscode format, and seems popular elsewhere.
This commit does nothing but reformat.

Part of #387

This enum was otiose: its set of valid values is precisely those of a
Vec.  (Indeed what would TokVal::Multi(vec![]) have meant?)

I ought to have c&p these.

As per
  tpo/core/arti!403 (comment 2786099)

This does not constitute any kind of stable API promise.
But it might allow people to use our arti client code in novel ways.

This is just code motion and the minimal fixups.

std::slice::from_ref exists.  Spotted while reviewing !400

Make ArtiConfigBuilder contain a TorClientConfigBuilder

See merge request tpo/core/arti!401

Follow-up from arti!318

See merge request tpo/core/arti!402