[nabil1440]

Change

• wp and exec stop the parse of fly flags at the first argument. All later arguments go to wp-cli or to the command without change.
• exec uses the PHP service of the site by default: php, or openlitespeed on OpenLiteSpeed sites. wp uses the same detection (docker.DefaultService).
• exec with only a service name shows an error.
• logs accepts -f/--follow, --tail and more than one service.
• The README tells how flags go to the command and where --domain goes.

Behavior change

• Put --domain before the wp-cli command or the exec command, for example fly --domain example.com wp plugin list. After the command, --domain goes to wp-cli.
• To send a flag as the first wp-cli argument, use --, for example fly wp -- --info.

Tests

• Unit tests: splitService, and DefaultService for php, openlitespeed, both and none.
• End-to-end tests examine the exact docker arguments for:
  • wp plugin list --format=json
  • --domain example.com wp plugin list --format=json
  • exec php ls -la and exec ls -la
  • exec ls and wp plugin list on an OpenLiteSpeed site
  • logs -f php and logs --tail 50
• These tests fail on the code before this PR. The only exception is wp on an OpenLiteSpeed site, which Fix(ols): Fix cli not detecting OLS sites #1 corrected.
• Real Docker: fly exec php ls -la …, fly exec cat … and fly logs --tail 3 php.

Closes #4