Sort new fields in lexicographic order during update

[wazir-ahmed]

Description

Closes #2038.

Readiness checklist

• I added/updated unit tests (and they pass).
• I added/updated integration/compatibility tests (and they pass).
• I added/updated comments and checked rendering.
• I made spot refactorings.
• I updated user documentation.
• I ran task all, and it passed.
• I ensured that PR title is good enough for the changelog.
• (for maintainers only) I set Reviewers (@FerretDB/core), Milestone (Next), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

Attention: Patch coverage is 88.52989% with 71 lines in your changes are missing coverage. Please review.

Project coverage is 74.12%. Comparing base (fb4f384) to head (3e04a0d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4223      +/-   ##
==========================================
- Coverage   75.33%   74.12%   -1.22%     
==========================================
  Files         323      323              
  Lines       22408    22355      -53     
==========================================
- Hits        16882    16571     -311     
- Misses       4306     4574     +268     
+ Partials     1220     1210      -10     

Files	Coverage Δ
internal/handler/common/update_array_operators.go	88.05% <87.09%> (+1.86%)	⬆️
internal/handler/common/update.go	91.69% <89.48%> (+1.14%)	⬆️

... and 36 files with indirect coverage changes

Flag	Coverage Δ
filter-false	?
filter-true	67.14% <88.52%> (-1.59%)	⬇️
hana-1	?
integration	67.14% <88.52%> (-1.64%)	⬇️
mongodb-1	5.13% <0.00%> (+0.01%)	⬆️
mysql-1	?
mysql-2	?
mysql-3	?
postgresql-1	44.95% <55.41%> (-7.01%)	⬇️
postgresql-2	43.87% <49.43%> (-9.63%)	⬇️
postgresql-3	42.77% <52.98%> (-10.78%)	⬇️
postgresql-4	41.23% <26.49%> (+0.41%)	⬆️
postgresql-5	43.34% <25.68%> (-2.51%)	⬇️
sqlite-1	43.92% <55.41%> (-7.11%)	⬇️
sqlite-2	43.19% <49.43%> (-9.43%)	⬇️
sqlite-3	42.01% <52.98%> (-10.67%)	⬇️
sqlite-4	40.62% <26.49%> (+0.51%)	⬆️
sqlite-5	42.47% <25.68%> (-2.34%)	⬇️
unit	31.96% <0.00%> (+0.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[chilagrow]

Thanks for your contribution 🤗

This is a huge change, we are taking time to review it carefully. Meanwhile I have a few questions 😃

[chilagrow]

Huge thanks for your contribution 🤗

[AlekSi]

Thank you!