mitmproxy: Update to 7.0.0

Changes:
## 16 July 2021: mitmproxy 7.0.0

### New Proxy Core (@mhils, [blog post](https://www.mitmproxy.org/posts/releases/mitmproxy7/))

Mitmproxy has a completely new proxy core, fixing many longstanding issues:

* **Secure Web Proxy:** Mitmproxy now supports TLS-over-TLS to already
  encrypt the connection to the proxy.
* **Server-Side Greetings:** Mitmproxy now supports proxying raw TCP
  connections, including ones that start with a server-side greeting (e.g. SMTP).
* **HTTP/1 – HTTP/2 Interoperability:** mitmproxy can now accept an
  HTTP/2 connection from the client, and forward it to an HTTP/1 server.
* **HTTP/2 Redirects:** The request destination can now be changed on
  HTTP/2 flows.
* **Connection Strategy:** Users can now specify if they want mitmproxy
  to eagerly connect upstream or wait as long as possible. Eager
  connections are required to detect protocols with server-side
  greetings, lazy connections enable the replay of responses without
  connecting to an upstream server.
* **Timeout Handling:** Mitmproxy will now clean up idle connections
  and also abort requests if the client disconnects in the meantime.
* **Host Header-based Proxying:** If the request destination is
  unknown, mitmproxy now falls back to proxying based on the Host
  header. This means that requests can often be redirected to mitmproxy
  using DNS spoofing only.
* **Internals:** All protocol logic is now separated from I/O
  (["sans-io"](https://sans-io.readthedocs.io/)).
  This greatly improves testing capabilities, prevents a wide array of
  race conditions, and increases proper isolation between layers.

### Additional Changes

* mitmproxy's command line interface now supports Windows (@mhils)

* The `clientconnect`, `clientdisconnect`, `serverconnect`,
  `serverdisconnect`, and `log` events have been replaced with new
  events, see addon documentation for details (@mhils)

* Contentviews now implement `render_priority` instead of
  `should_render`, allowing more specialization (@mhils)
* Addition of block_list option to block requests with a set status
  code (@ericbeland)
* Make mitmweb columns configurable and customizable (@gorogoroumaru)
* Automatic JSON view mode when `+json` suffix in content type (@kam800)
* Use pyca/cryptography to generate certificates, not pyOpenSSL (@mhils)
* Remove the legacy protocol stack (@Kriechi)
* Remove all deprecated pathod and pathoc tools and modules (@Kriechi)
* In reverse proxy mode, mitmproxy now does not assume TLS if no scheme
  is given but a custom port is provided (@mhils)
* Remove the following options: `http2_priority`,
  `relax_http_form_validation`, `upstream_bind_address`,
  `spoof_source_address`, and `stream_websockets`. If you depended on
  one of them please let us know.  mitmproxy never phones home, which
  means we don't know how prominently these options were used. (@mhils)
* Fix IDNA host 'Bad HTTP request line' error (@grahamrobbins)
* Pressing `?` now exits console help view (@abitrolly)
* `--modify-headers` now works correctly when modifying a header that
  is also part of the filter expression (@Prinzhorn)
* Fix SNI-related reproducibility issues when exporting to curl/httpie
  commands. (@dkasak)
* Add option `export_preserve_original_ip` to force exported command to
  connect to IP from original request.
  Only supports curl at the moment. (@dkasak)
* Major proxy protocol testing (@r00t-)
* Switch Docker image release to be based on Debian (@PeterDaveHello)
* Multiple Browsers: The `browser.start` command may be executed more
  than once to start additional browser sessions. (@rbdixon)
* Improve readability of SHA256 fingerprint. (@wrekone)
* Metadata and Replay Flow Filters: Flows may be filtered based on
  metadata and replay status. (@rbdixon)
* Flow control: don't read connection data faster than it can be
  forwarded. (@hazcod)
* Docker images for ARM64 architecture (@hazcod, @mhils)
* Fix parsing of certificate issuer/subject with escaped special
  characters (@Prinzhorn)
* Customize markers with emoji, and filters: The `flow.mark` command
  may be used to mark a flow with either the default "red ball" marker,
  a single character, or an emoji like `:grapes:`.  Use the `~marker`
  filter to filter on marker characters. (@rbdixon)
* New `flow.comment` command to add a comment to the flow. Add
  `~comment <regex>` filter syntax to search flow comments. (@rbdixon)
* Fix multipart forms losing `boundary` values on edit. (@roytu)
* `Transfer-Encoding: chunked` HTTP message bodies are now retained if
  they are below the stream_large_bodies limit. (@mhils)
* `json()` method for HTTP Request and Response instances will return
  decoded JSON body. (@rbdixon)
* Support for HTTP/2 Push Promises has been dropped. (@mhils)
* Make it possible to set sequence options from the command line. (@Yopi)


(leot)