Productivity Analytics: Add yAxis formatter to column charts

What does this MR do?

This MR adds a default formatter for the yAxis for column charts on the Productivity Analytics page. By this, the value is display on the axis without any additional formatting. In detail, It fixes an issue where 500m is displayed as y axis label instead of 0.5 which seems to be caused by echarts transforming certain axis label values.

Closes #32054 (closed)

This is behind the productivity_analytics feature flag.

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Before	After

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team