Store repo size (in kB) in database

[rmunn]

Fix #1088.

Work completed:

• hg command runner command to get the repo size in kilobytes (it'll always be a multiple of 4 kb, so getting it in bytes isn't really necessary).
• store size in Project table
• update size after each Send/Receive
• GQL mutation to update project size
• frontend updates project size automatically if it's null
  • GQL mutation has CanViewProject permissions, so this will work no matter who's viewing the project page

Screenshot:

[github-actions[bot]]

C# Unit Tests

90 tests  +15   90 :white_check_mark: +15   5s :stopwatch: ±0s 14 suites + 1    0 :zzz: ± 0   1 files   ± 0    0 :x: ± 0 

Results for commit b5b8cbdb. ± Comparison against base commit 85f9555f.

:recycle: This comment has been updated with latest results.

[github-actions[bot]]

UI unit Tests

12 tests   12 :white_check_mark:  0s :stopwatch:  4 suites   0 :zzz:  1 files     0 :x:

Results for commit b5b8cbdb.

:recycle: This comment has been updated with latest results.

[rmunn]

Note: currently this does not add an "update" button like the others; instead, the frontend project page automatically issues the updateRepoSizeInKb mutation request if the size is null. That would display a spinner while it updates, but it's so fast (even on the elawa-dev-flex repo) that I've never actually seen the spinner during my testing.

But if we want to change this to have the "update" button accessible only to admins (or to project managers?) then I can do that.

[rmunn]

Rebased on top of develop to fix FwHeadless build issue fixed in #1217.