chore: remove clicompat help templates and use urfave/cli defaults

[burmudar]

When migrating the abc command, it became apparent that the help rendering can quickly become annoying. It's better for us to just rely on the urfave/cli defaults.

Yes, there will be some visible inconsistency in help outputs now but in the long run I think it helps, since it requires less cognitive load to review + migrate a command.

Changes

• remove custom help templates
• remote WrapRoot and WithLegacyHelp
• fixup version command to have better help formatting with urfave defaults

Test plan

src version old

Usage of 'src version':
  -client-only
        If true, only the client version will be printed.
  -dump-requests
        Log GraphQL requests and responses to stdout
  -get-curl
        Print the curl command for executing this query and exit (WARNING: includes printing your access token!)
  -insecure-skip-verify
        Skip validation of TLS certificates against trusted chains
  -trace
        Log the trace ID for requests. See https://docs.sourcegraph.com/admin/observability/tracing
  -user-agent-telemetry
        Include the operating system and architecture in the User-Agent sent with requests to Sourcegraph (default true)

Examples:

  Get the src-cli version and the Sourcegraph instance's recommended version:

        $ src version

src version new

go run ./cmd/src version -h
NAME:
   src version

USAGE:
   src version [options]

DESCRIPTION:

   Display and compare the src-cli version against the recommended version for your instance

   Examples:

   Get the src-cli version and the Sourcegraph instance's recommended version:

   $ src version


OPTIONS:
   --client-only           If true, only the client version will be printed.
   --dump-requests         Log GraphQL requests and responses to stdout
   --get-curl              Print the curl command for executing this query and exit (WARNING: includes printing your access token!)
   --trace                 Log the trace ID for requests. See https://docs.sourcegraph.com/admin/observability/tracing
   --insecure-skip-verify  Skip validation of TLS certificates against trusted chains
   --user-agent-telemetry  Include the operating system and architecture in the User-Agent sent with requests to Sourcegraph
   --help, -h              show help