[ML] Error when trying to start ML job with bucket span 1w

[bwesely]

Kibana version:
7.7.0

Elasticsearch version:
7.7.0

Server OS version:
Docker Desktop on macOS

Browser version:
Chrome Version 80.0.3987.163 (Official Build) (64-bit)

Browser OS version:
Version 80.0.3987.163 (Official Build) (64-bit)

Original install method (e.g. download page, yum, from source, etc.):
Official Docker image

Description of the problem including expected versus actual behavior:
Creating a Machine Learning job with Bucket Span: 1w fails with an error
When entering 1d, 2d,... 7d is working as expected.

Steps to reproduce:

1. Create Anomaly Job with sum(field) over a couple of years
2. Set Bucket Span to 1w
3. Continue to Validation Step
4. Error is shown

Errors in browser console (if relevant):

Error: Job Validation Error: Bad Request
    at Object.errorNotify [as error] (http://localhost:5601/bundles/plugin/ml/1.plugin.js:1:1602697)
    at http://localhost:5601/bundles/plugin/ml/1.plugin.js:1:33434

Provide logs and/or server output (if relevant):

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[peteharverson]

Week units w are not valid for bucket spans - we only support s, m, h and d, plus ms if it is an exact multiple of 1000. This is core Elasticsearch functionality for time durations - see https://github.com/elastic/elasticsearch/blob/e9bc3e8234b4f1a3785101481a46e01541f8fdaf/libs/core/src/main/java/org/elasticsearch/common/unit/TimeValue.java#L357-L387.

However the validation used in the job wizards is currently allowing w, M and y to be used in the bucket span input. This should be changed to prevent units other than s, m, h and d (plus ms if a multiple of 1000).

Note on master the following error is displayed if entering 1w for the bucket span. But the user is allowed to continue to the next step of the wizard, with the error shown in the toast notification not making it clear that w is not a valid time interval unit.

The solution here should be to fix the client-side validation to prevent w, M and y as bucket span units.