Revert "slaprunner: fix resiliency test, add development-mode (bool) parameter for easy build webrunner in webrunner"

This reverts commit 59966611.

hosts-dict values cannot be domain names.
memcached entries are implementation-independent (no mention of kumofs
anymore).
relational database information (which does not follow above memcached
rule, sadly, naming mariadb explicitly) is published in two lists.
Add minimal patterns to document what requester should expect.
Document deadlock-debugger-password".
Drop non-standard "optional" property from jupyter-url declaration.

slaprunner: fix resiliency test, add development-mode (bool) parameter for easy build webrunner in webrunner

This is backported to ZODB-3.10 https://github.com/zopefoundation/persistent/pull/44

The patch is needed for wendelin.core to being able to relase not needed
memory.

/reviewed-on nexedi/slapos!93

This reverts commit 605e564b.

Rationale: Stability matters:

Quoting 605e564b:
> Besides changing only recv window size at runtime breaks compatibility with
> openssh: if we only do `-W 1M` on server and try to upload data with openssh as
> client, dropbear complains
>
>     [3302] Apr 17 23:10:06 Exit (slapuser2): Bad packet size 32777
>
> and connection terminates. Thus RECV_MAX_PAYLOAD_LEN increase is also
> required, which cannot be done via option at runtime:
>
>     https://github.com/mkj/dropbear/blob/DROPBEAR_0.53.1/options.h#L268
>
>     ---- 8< ----
>     /* Maximum size of a received SSH data packet - this _MUST_ be >= 32768
>        in order to interoperate with other implementations */
>     #ifndef RECV_MAX_PAYLOAD_LEN
>     #define RECV_MAX_PAYLOAD_LEN 32768
>     #endif
>     ---- 8< ----
>
> So let's increase DEFAULT_RECV_WINDOW to 1M and RECV_MAX_PAYLOAD_LEN
> appropriately (experimentally found that at 512K the complain goes
> away).

It turned out that "Bad packet size" did not really went away. For example I've
recently hit the following:

    [14586] Aug 04 19:12:43 Pubkey auth succeeded for 'slapuser16' with key md5 b1:35:06:d3:a5:b1:0b:c6:7f:e6:59:31:ab:3a:e1:56 from 2001:67c:1254:c0::1:49886
    [14586] Aug 04 19:12:55 Exit (slapuser16): Integrity error (bad packet size 524500)

in .slappartX_runner_sshd.log of my upgraded webrunner with connection being broken.
( nexedi/slapos!68 (comment 17748) )

We could maybe try to play games with increasing RECV_MAX_PAYLOAD_LEN to
be more than DEFAULT_RECV_WINDOW but this already turned out to be error-prone.

Since when really needed we should be able to replace dropbear with openssh

    nexedi/slapos!68 (comment 7082)

which is both performant and good-compatible, to me the way is:

- make current dropbear run stable again,
- when we really need to sync large amounts of data (and we should be
  needing to do soon or already) -> work on replacing dropbear with
  openssh.

- GitLab Software + patches ported to GitLab 8.7.X;
- Configs synced with upstream;
- No base software upgrades this time because it was all recently
  upgraded during a590b03e;

TODO: allow configuration of trusted proxies

/reviewed-by TrustMe

Like for 2a835e63

    $ git diff 8.6.5+ce.0-0-g342f8be..8.7.9+ce.1-0-gf589ad7 --
            files/gitlab-cookbooks/gitlab/templates/default/sv-sidekiq-run.erb

is empty.