remove --help, fix help command for flags

[geyslan]

Close #3299

1. Explain what the PR does

b549093 fix(flags)!: remove --help, fix help command _{(2023/jul/06) Geyslan Gregório <geyslan@gmail.com>}

The --help workaround for flags is removed, and the help command is
fixed to work as expected for both commands and flags.

BREAKING CHANGE: --help is no longer supported for flags. Use:
 - "tracee [command] --help" for more information about a command.
 - "tracee help [command|flag]" for more information about a command or
    flag.

2. Explain how to test it

Ask for a command help list (generated by cobra):

./dist/tracee help list

List traceable events

Usage:
  tracee list

Aliases:
  list, l

Flags:
      --signatures-dir stringArray   Directories where to search for signatures in CEL (.yaml), OPA (.rego), and Go plugin (.so) formats

Ask for a flag help --config (our own text, since cobra doesn't provide help cmd for flags):

./dist/tracee help config

The --config flag allows you to define global configuration options (flags)
for tracee, by providing a file in YAML or JSON format between others (see documentation).

All flags can be set in the config file, except for the following, which are reserved only
for the CLI:
  --config (this flag)
  --capture
  --policy

The --filter flag also cannot be set in the config file since it's reserved for the CLI
and the policy file loading mechanism (via the --policy flag).

Ask for a general help (generated by cobra based on specified template):

./dist/tracee help

Tracee uses eBPF technology to tap into your system and give you
access to hundreds of events that help you understand how your system behaves.

Usage:
  tracee [flags]
  tracee [command]

Available Commands:
  analyze     Analyze past events with signature events [Experimental]
  completion  Generate the autocompletion script for the specified shell
  help        Help about any command or flag
  list        List traceable events
  version     Print the version number of Tracee

Flags:
  -f, --filter stringArray           Select events to trace by defining filter expressions
  -p, --policy stringArray           Path to a policy or directory with policies
  -o, --output stringArray           Control how and where output is printed (default [table])
  -c, --capture stringArray          Capture artifacts that were written, executed or found to be suspicious
      --config string                Global config file (yaml, json between others - see documentation)
      --containers                   Enable container info enrichment to events. This feature is experimental and may cause unexpected behavior in the pipeline
      --crs stringArray              Define connected container runtimes
      --signatures-dir stringArray   Directories where to search for signatures in CEL (.yaml), OPA (.rego), and Go plugin (.so) formats
      --rego stringArray             Control event rego settings
  -b, --perf-buffer-size int         Size, in pages, of the internal perf ring buffer used to submit events from the kernel (default 1024)
      --blob-perf-buffer-size int    Size, in pages, of the internal perf ring buffer used to send blobs from the kernel (default 1024)
  -a, --cache stringArray            Control event caching queues (default [none])
      --metrics                      Enable metrics endpoint
      --healthz                      Enable healthz endpoint
      --pprof                        Enable pprof endpoints
      --pyroscope                    Enable pyroscope agent
      --listen-addr string           Listening address of the metrics endpoint server (default ":3366")
  -C, --capabilities stringArray     Define capabilities for tracee to run with
      --install-path string          Path where tracee will install or lookup it's resources (default "/tmp/tracee")
  -l, --log stringArray              Logger options (default [info])

Use:
  "tracee [command] --help" for more information about a command.
  "tracee help [command|flag]" for more information about a command or flag.

3. Other comments

It's important to note that --help continues to function as a flag for commands.

[geyslan]

@yanivagman, as we discussed in today's meeting, due to change of plans, I'm closing this and pushing soon a new solution with:

• removal of help command
• --help flag would just output the default help output with all commands and flags summarised
• move all flags help text to respective markdowns (this will solve the scope and event flags documentation split - Events and Scope flags #3262 (comment), Events and Scope flags #3262 (comment)).

In a further PR, we can add pandoc or other tool to convert the markdowns to man pages during the package build etc. @rafaeldtinoco FYI