ci(stage-build): rsync with -j html,json,txt

[caugner]

Summary

Part of MP-315.

Problem

The GCP deployment is still slow, and copying client/build takes longer than it used to take in AWS.

Solution

Accelerate the storage copy using the -j option:

Applies gzip transport encoding to any file upload whose extension matches the -j extension list. This is useful when uploading files with compressible content (such as .js, .css, or .html files) because it saves network bandwidth while also leaving the data uncompressed in Cloud Storage. (Source)

Note: json, html and txt are by far the most frequent text formats in the build.

% find . -type f | sed -e 's/.*\.//' | sort | uniq -c | sort -nr
81115 json
52112 html
40502 txt
2146 png
 276 jpg
 218 svg
  85 gif
  32 map
  21 js
  12 css
   9 gz
   2 xml
   2 woff2
   1 jpeg
   1 ico

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How did you test this change?

• Before: 10m/AWS vs 25m/GCP
• After: 3m/AWS vs 3m/GCP

[caugner]

For my tests above I used a 4-core large runner, but I want to ensure that the stage-build time does not regresses with the standard 2-core runners either, so I have marked this PR as draft while this stage-build is running.

[caugner]

@bkochendorfer Wow, 42m for build + sync to AWS + sync to GCP!