Merge lp://staging/~mthaddon/charm-haproxy/jammy into lp://staging/charm-haproxy

Add support for jammy

Add support for jammy.

I've done a test install of all supported series, and then also confirmed I can relate the new pollen charm to the HAProxy charm on jammy and can query both:

```
mthaddon@finistere:~/repos/haproxy-charm/charm-haproxy$ pollinate -i -s http://10.46.16.58:80 -t
<13>Jul 13 11:57:44 pollinate[1641944]: client sent challenge to [http://10.46.16.58:80]
<13>Jul 13 11:57:44 pollinate[1641944]: client verified challenge/response with [http://10.46.16.58:80]
�!ȹ��
�E������W�<QQ^Ȥ���%��lxg��&�$�ׄ�Y�(�àH2�]J<13>Jul 13 11:57:44 pollinate[1641944]: client hashed response from [http://10.46.16.58:80]
<13>Jul 13 11:57:44 pollinate[1641944]: client successfully seeded [-]
mthaddon@finistere:~/repos/haproxy-charm/charm-haproxy$ # That's jammy
mthaddon@finistere:~/repos/haproxy-charm/charm-haproxy$ pollinate -i -s http://10.46.16.213:8080 -t
<13>Jul 13 11:57:59 pollinate[1642040]: client sent challenge to [http://10.46.16.213:8080]
<13>Jul 13 11:57:59 pollinate[1642040]: client verified challenge/response with [http://10.46.16.213:8080]
)8�U��~��4D���0�$m�<�/:ѾnIN�$-4JM+⨷4�ך�A��G]���"N��g��<13>Jul 13 11:57:59 pollinate[1642040]: client hashed response from [http://10.46.16.213:8080]
<13>Jul 13 11:57:59 pollinate[1642040]: client successfully seeded [-]
mthaddon@finistere:~/repos/haproxy-charm/charm-haproxy$ # And that's the pollen unit
mthaddon@finistere:~/repos/haproxy-charm/charm-haproxy$ juju status
Model Controller Cloud/Region Version SLA Timestamp
default localhost-localhost localhost/localhost 2.9.43 unsupported 11:59:15+02:00

App Version Status Scale Charm Channel Rev Exposed Message
bionic active 1 haproxy 0 no Unit is ready
focal active 1 haproxy 0 no Unit is ready
jammy active 1 haproxy 0 no Unit is ready
pollen active 1 pollen edge 3 no
xenial active 1 haproxy 0 no Unit is ready

Unit Workload Agent Machine Public address Ports Message
bionic/0* active idle 1 10.46.16.31 Unit is ready
focal/0* active idle 2 10.46.16.176 Unit is ready
jammy/0* active idle 3 10.46.16.58 80/tcp Unit is ready
pollen/0* active idle 4 10.46.16.213
xenial/0* active idle 0 10.46.16.28 Unit is ready

Machine State Address Inst id Series AZ Message
0 started 10.46.16.28 juju-72706c-0 xenial Running
1 started 10.46.16.31 juju-72706c-1 bionic Running
2 started 10.46.16.176 juju-72706c-2 focal Running
3 started 10.46.16.58 juju-72706c-3 jammy Running
4 started 10.46.16.213 juju-72706c-4 jammy Running

mthaddon@finistere:~/repos/haproxy-charm/charm-haproxy$
```