Bump StateDB to v0.3.4 and refactor db command usages

[joamaki]

To improve the ergonomics of the 'help' command in cilium shell I've decided to avoid nested
sub-commands (e.g. "db show") and instead go for Plan 9 style flat "db/show" commands.
This way the 'help' command can list all the commands and 'help -v' can give extended help
for the commands.

This PR bumps StateDB to v0.3.4 which comes with the new style and refactors the usages
of the commands in tests and mentions in docs.

While at it, I changed also the experimental LB to use the same style and to modify it so it won't
register its tables or commands unless enabled to avoid confusion.

Help now looks like this:

cilium> help
[stdout]

commands:

cat files...
        concatenate files and print to the script's stdout buffer
db
        Describe StateDB configuration
db/cmp [-timeout=<dur>] [-grep=<pattern>] table file
        Compare table
db/delete table path...
        Delete an object from the table
db/get [-o=<file>] [-columns=col1,...] [-format={table*,yaml,json}] [-index=<index>] table key
        Get the first matching object
db/initialized [-timeout=<duration>] table...
        Wait until all or specific tables have been initialized
db/insert table path...
        Insert object into a table
db/list [-o=<file>] [-columns=col1,...] [-format={table*,yaml,json}] [-index=<index>] table key
        List objects in the table
db/lowerbound [-o=<file>] [-columns=col1,...] [-format={table*,yaml,json}] [-index=<index>] table key
        Query table by lower bound search
db/prefix [-o=<file>] [-columns=col1,...] [-format={table*,yaml,json}] [-index=<index>] table key
        Query table by prefix
db/show [-o=<file>] [-columns=col1,...] [-format={table,yaml,json}] table
        Show the contents of a table
db/watch table
        Watch a table for changes
exec program [args...] [&]
        run an executable program with arguments
help [-v] name...
        log help text for commands and conditions
lb/prune
        Trigger pruning of LB maps
lb/maps-dump (output file)
        Dump the load-balancing BPF maps
lb/maps-restore
        Restore the load-balancing BPF maps from snapshot
lb/maps-snapshot
        Snapshot the load-balancing BPF maps

And we now can get verbose help for the commands:

cilium> help db/show
[stdout]
db/show [-o=<file>] [-columns=col1,...] [-format={table,yaml,json}] table
        Show the contents of a table

        Show the contents of a table.

        The contents are written to stdout, but can be written to
        a file instead with the -o flag.

        By default the table is shown in the table format.
        For YAML use '-format=yaml' and for JSON use '-format=json'

        To only show specific columns use the '-columns' flag. The
        columns are as specified by 'TableHeader()' method.
        This flag is only supported with 'table' formatting.

[joamaki]

/test

[joamaki]

/test

[joamaki]

/test

[pippolo84]

✔️

[joamaki]

/test

[dylandreimerink]

LGTM

[joestringer]

LGTM, thanks!

[tommyp1ckles]

CLI changes looks good

[joamaki]

/test