[DPE-10892] Add scripting and caching permissions

[reneradoi]

This PR addresses:

• Scripting permissions #82
• Grant client|id, client|tracking and ping to valkey_client relation users #88

The permissions for external client users are adjusted to allow client-side caching and LUA scripting. To safeguard memory consumption for client-side caching, the configuration tracking-table-max-keys is explicitly set to 1M (same as default).

Regarding scripting: The scripting permissions do not impact the keyspace permissions, or in other words: Scripts can only be executed on a key if the user has permissions for it. This was confirmed by testing:

$ juju deploy data-integrator
$ juju deploy ./valkey_ubuntu@24.04-amd64.charm --trust --resource valkey-image=ghcr.io/canonical/charmed-valkey:9.0.1-26.04_edge
$ juju config data-integrator prefix-name="test:*"
$ juju integrate data-integrator valkey                                                                             
$ valkey-cli -h 10.1.0.12 -p 6379
10.1.0.12:6379> auth relation-5-ee6157ff1cd25188 <password>
OK                                                                
10.1.0.12:6379> set mykey 42
(error) NOPERM No permissions to access a key
10.1.0.12:6379> set test:mykey 42
OK
10.1.0.12:6379> get mykey
(error) NOPERM No permissions to access a key
10.1.0.12:6379> get test:mykey
"42"
10.1.0.12:6379> EVAL "return server.call('SET', KEYS[1], ARGV[1])" 1 foo bar
(error) NOPERM No permissions to access a key
10.1.0.12:6379> EVAL "return server.call('SET', KEYS[1], ARGV[1])" 1 test:foo bar
OK
10.1.0.12:6379> EVAL "return server.call('GET', KEYS[1])" 1 foo
(error) NOPERM No permissions to access a key
10.1.0.12:6379> EVAL "return server.call('GET', KEYS[1])" 1 test:foo
"bar"