feat: add calculate default maps size by session - #622

Since edgecomllc#622 an unset map size is derived from max_sessions, whose default
is 65535: PDR, FAR and URR maps of 131,070 entries and a QER map of
65,535. Those maps are allocated at startup and charged to the pod, about
115 MiB, a working set of about 140 MiB with the process. The chart's
default memory limit is 128 Mi, set for the 1024-entry maps of the 0.7.1
image, so an image built from main fails at startup with the chart's
defaults: "creating map: map create: cannot allocate memory".

The chart now sets UPF_MAX_SESSIONS to 1024 in defaultEnv, which keeps the
maps at the size the limit was set for (a working set of about 30 MiB),
and the README says how max_sessions and the memory limit scale together:
about 1.8 MiB per 1024 sessions on top of the process's ~30 MiB. In
ConfigMap mode max_sessions goes into config.data, since the default
variables are not injected there.

Measured on a kind cluster with the kubelet's accounting: main's defaults
start under 192 Mi and above, not under 128 Mi; with UPF_MAX_SESSIONS=1024
the pod starts under 128 Mi and passes the same tests as 0.7.1.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Signed-off-by: Martin Matyas <[email protected]>

Since edgecomllc#622 an unset map size is derived from max_sessions, whose default
is 65535: PDR, FAR and URR maps of 131,070 entries and a QER map of
65,535. Those maps are allocated at startup and charged to the pod, about
115 MiB, a working set of about 140 MiB with the process. The chart's
default memory limit is 128 Mi, set for the 1024-entry maps of the 0.7.1
image, so an image built from main fails at startup with the chart's
defaults: "creating map: map create: cannot allocate memory".

The chart now sets UPF_MAX_SESSIONS to 1024 in defaultEnv, which keeps the
maps at the size the limit was set for (a working set of about 30 MiB),
and the README says how max_sessions and the memory limit scale together:
about 1.8 MiB per 1024 sessions on top of the process's ~30 MiB. In
ConfigMap mode max_sessions goes into config.data, since the default
variables are not injected there.

Measured on a kind cluster with the kubelet's accounting: main's defaults
start under 192 Mi and above, not under 128 Mi; with UPF_MAX_SESSIONS=1024
the pod starts under 128 Mi and passes the same tests as 0.7.1.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Signed-off-by: Martin Matyas <[email protected]>