AutoML: allow access to get_leaderboard as a method of aml instance

[exalate-issue-sync]

Access to extended leaderboard using {{h2o.automl.get_leaderboard(...)}} is currently only accessible as a global function in Py (symmetry with R implementation).
Following commong Py usage, it should however also be accessible as a method of any automl instance:

{code:python}aml = H2OAutoML(…)
aml.train(…)
ext_lb = aml.get_leaderboard('ALL'){code}

[h2o-ops-ro]

JIRA Issue Details

Jira Issue: PUBDEV-8343
Assignee: Sebastien Poirier
Reporter: Sebastien Poirier
State: Resolved
Fix Version: 3.34.0.3
Attachments: N/A
Development PRs: Available

[h2o-ops-ro]

Linked PRs from JIRA

#5781