Add create and update time to Measurement

[roaminggypsy]

Make it easier to filter Measurements for prober

[wfa-reviewable]

This change is 

[SanjayVas]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @roaminggypsy and @stevenwarejones)

---

src/main/proto/wfa/measurement/api/v2alpha/measurement.proto line 365 at r1 (raw file):

      [(google.api.field_behavior) = OUTPUT_ONLY];

  // When the 'Measurement' was lastly updated.

Suggestion:

last

[roaminggypsy]

Reviewable status: 1 of 2 files reviewed, 1 unresolved discussion (waiting on @SanjayVas and @stevenwarejones)

---

src/main/proto/wfa/measurement/api/v2alpha/measurement.proto line 365 at r1 (raw file):

      [(google.api.field_behavior) = OUTPUT_ONLY];

  // When the 'Measurement' was lastly updated.

Done.

[SanjayVas]

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @stevenwarejones)

[stevenwarejones]

I'm surprised we didn't already have these.

Reviewed 1 of 2 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @roaminggypsy)

[roaminggypsy]

yeah. I was hesitating whether I can add these fields because I thought there were intentionally not exposed. It turned out that it is just because previous work did not need such fields.

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @roaminggypsy)