feat: support passing license as file

[arkbriar]

Explanation in Detail

Note

Same as what we did in risingwavelabs/risingwave-operator#732, the environment variable used to pass the file path is RW_LICENSE_KEY_PATH due to a mistake in the original PR.

• Add an option .license.passAsFile in the values to allow explicitly enabling the feature in feat(meta): watch and reload license key from file risingwave#18768.
• The PR maintains backward compatibility.

Example values (tested locally)

metaStore:
  sqlite:
    enabled: true
    
stateStore:
  localFs:
    enabled: true

standalone:
  enabled: true

license:
  secret:
    name: license
    key: license.jwt
  passAsFile: true

image:
  registry: ghcr.io
  repository: risingwavelabs/risingwave
  tag: nightly-20241009

Expectations

• select rw_test_paid_tier() returns t instead of an error message when a valid license is specified.

Future works

• When the v2.1 is released, passAsFile will be marked as deprecated in the next helm chart release.
• When the v2.2 is released, passAsFile will be removed as well as all the related branches.