The list of changes is available here:

https://github.com/mozilla/glean/releases/tag/v19.1.0

Mostly bugfixes ;)

This removes the Kotlin implementation from this repository
and introduces type aliases that point to the Rust implementation,
which is now a new dependency.

There's some confusion in `GeckoEngineSession` about redirect flags.
The `VISIT_REDIRECT_SOURCE` and `VISIT_REDIRECT_SOURCE_PERMANENT` flags
that we get from GeckoView's history delegate are for the redirect
_source_, not the visit type. They indicate if the URL passed to
`onVisited` is redirecting _to_ another URL, most likely because the
server returned an HTTP 3xy status code with a `Location` header.
Rust Places decides whether to mark the URL as hidden based on
these flags.

`VISIT_REDIRECT_{PERMANENT, TEMPORARY}`, however, indicate if the
URL passed to `onVisited` is the _target_ of a redirect (in other
words, the page that's _in_ the `Location` header). These get
translated into `VisitType` flags, which Rust Places stores as the
visit transition type. These two flags don't affect whether a URL
is hidden.

Note that, in a redirect chain, the middle links are both sources and
targets. For example, in "mozilla.org" -> "www.mozilla.org" ->
"www.mozilla.org/en-US", "www.mozilla.org" is both a redirect target
(since "mozilla.org" redirected to it), and a source (it redirected
to "www.mozilla.org/en-US").

See mozilla-mobile/fenix#3526.