[Lens] Fix time shift usability issues

[flash1293]

Fixes #102116
Fixes #102405

This PR fixes a few usability issues with time shift in Lens:

• Allow space between amount and time unit
• Change "previous" label to "previous time range"
• Add "ago" to option labels
• Change placeholder to encourage typing (see [Lens] Improve time shift's "custom" interval discoverability #102116 (comment))

I'm not sure about the placeholder change. We thought about something like "Enter a time shift. Type to specify custom values (e.g. 8w)" but the space is way to tight for that. The best i could do is "Type custom values (e.g. 8w)", but even that won't be visible on all screen widths:

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[wylieconlon]

For the space issue, you could use the helpText property instead of placeholder. What do you think about explaining only the custom option as part of helpText?

[ghudgins]

What do you think about explaining only the custom option as part of helpText?

@wylieconlon the problem with this is the dropdown covers the helper text and, as soon as you click "time shift" in the popover, we move the user into the dropdown for fewer clicks & what I assume are good accessibility reasons.

I think Type custom value gets the important part across (type) even if it gets clipped. Not sure about other languages of course. But either way the placeholder seems better than what it is now which is redundant Time shift

[flash1293]

@elasticmachine merge upstream

[flash1293]

@wylieconlon @ghudgins If you are happy with this solution, I am happy - I think it's better than the current placeholder and we can give it a shot and see whether this problem is still happening.

[dej611]

Code LGTM. Tested locally 👍

[wylieconlon]

LGTM

[flash1293]

@elasticmachine merge upstream

[streamich]

AppServices regular expression change LGTM.

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 65741c8
• Storybooks Preview

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
lens	1.5MB	1.5MB	+59.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
data	831.2KB	831.2KB	+3.0B

History

• 💚 Build #133016 succeeded 92f076b
• 💚 Build #132595 succeeded 691dd3b

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@elasticmachine merge upstream

[kibanamachine]

💚 Backport successful

Status	Branch	Result
✅	7.x

This backport PR will be merged automatically after passing CI.