[Lens] allow synonyms and spaces in time shift intervals configuration

[ghudgins]

Describe the feature:
During usability testing someone attempted 8 w and 8 wk as a shift interval. We should allow the spaces as a valid input if we are able. Would be nice to handle common synonyms and fully typed out intervals like mon month wk week day yr year qtr quarter. Might also be good to allow the plural on all fully spelled out variants months weeks days years quarters

Describe a specific use case for the feature:
A user entering a number can naturally enter a space between the number ("8") and the interval unit ("w") without thinking if it matches the time shift syntax which expects no space. we should remove spaces for them and allow this as a valid configuration

A user enters the full name of the interval (plus a space) like "8 weeks" and expects the "8w" shift

[elasticmachine]

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

[ghudgins]

@markov00 mentions i18n (can we use translatable intervals via moment or something) and considering the word "ago" in the dropdown (example: 1 week ago)

this concept overall is sometimes referred to as time stamp humanization

[flash1293]

These are two separate things - the phrase 1 week ago in the dropdown is already translated. The underlying value is just 1w (and I don't think we should translate these as it will get very messy and I don't see a good reason for it - we also don't translate function names)

[markov00]

@flash1293 you are right, we were talking about time and ended up talking about that humanize the timestamp in general.
I think we just mess up with the ideas in this ticket

[ghudgins]

we aren't using the word ago in that dropdown. might be worth adding (since it'll get translated)