fix: define lowest deps correctly

[bshaffer]

The new check for installing lowest dependencies (#6899) found the following errors (yay!):

• AlloyDB needs a minimum of google/common-protos:4.4
• Channel needs a minimum ofgoogle/common-protos:3.2||4.0
• Core needs to use more recent versions of guzzlehttp/psr and monolog/monolog
• update root composer.json to match these changes

Additionally, I am adding the version field to google/longrunning, because otherwise it will constantly have issues with its circular dependency on google/gax.