Prompted by a compiler warning which I weirdly can't seem to reproduce?

ClientCirc: add functions to return the circuit's actual path

Closes #415

See merge request tpo/core/arti!419

Use less space in hashtables for microdescriptors

Closes #386

See merge request tpo/core/arti!415

Closes #415

Alternative API for set_isolation_group().

See merge request tpo/core/arti!418

Each channel now remembers an OwnedChanTarget.

Each circuit now remembers a vector of OwnedChanTarget to represent
the path that it was constructed for.

Part of #415.

This will help with #415

Instead of requiring a `Box<dyn Isolation>`, it now takes either a
`Box<dyn Isolation>`, or an arbitrary `T` that implements
`Isolation`.

This API still allows the user to pass in a `Box<dyn Isolation>` if
that's what they have, but it doesn't require them to Box the
isolation on their own.

Part of #414.

new api for isolation

See merge request tpo/core/arti!377

Absolish builders for CircMgrConfig and DirMgrConfig

See merge request tpo/core/arti!417

dirmgr: Always send if-modified-since on consensus documents.

Closes #403

See merge request tpo/core/arti!412

See rationale in the comment.

See commentary for the rationale.

Now we use NetParams.  That implies making its constructor public,
which I think it fine.

This is related to #413 but is far from completing that ticket.

This handwritten conversion function omitted a field.  There was
nothing to spot this mistake.

IMO this shows why these particular types ought not to use builders,
but instead, should cause API breaks when things change.

Adding this line here to explicitly fix the bug, although we are about
to abolish this function completely almost right away.

Fix typo

See merge request tpo/core/arti!416

it seems I added conditional compilation without noticing it??
and there was some errors when choosing a prefered runtime depending on
feature flags

this also removes JoinResult

the inverted logic was too easy to mess up