fix: LSDV-5425-1: Fix possible performance regression introduced in #4588

[jombooth]

PR fulfills these requirements

• Commit message(s) and PR title follows the format [fix|feat|ci|chore|doc]: TICKET-ID: Short description of change made ex. fix: DEV-XXXX: Removed inconsistent code usage causing intermittent errors
• Tests for the changes have been added/updated (for bug fixes/features)
• Docs have been added/updated (for bug fixes/features)
• Best efforts were made to ensure docs/code are concise and coherent (checked for spelling/grammatical errors, commented out code, debug logs etc.)
• Self-reviewed and ran all changes on a local instance (for bug fixes/features)

Change has impacts in these area(s)

(check all that apply)

• Product design
• Backend (Database)
• Backend (API)
• Frontend

Describe the reason for change

(link to issue, supportive screenshots etc.)

per discussion with @makseq, remove the new use of QuerySet#first() from #4588 in favor of fast_first. Also reimplement fast_first not to cache the entire queryset, but use a LIMIT 1 query.

What does this fix?

(if this is a bug fix)

What is the new behavior?

(if this is a breaking or feature change)

What is the current behavior?

(if this is a breaking or feature change)

What libraries were added/updated?

(list all with version changes)

Does this change affect performance?

(if so describe the impacts positive or negative)

Does this change affect security?

(if so describe the impacts positive or negative)

What alternative approaches were there?

(briefly list any if applicable)

What feature flags were used to cover this change?

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Does this PR introduce a breaking change?

(check only one)

• Yes, and covered entirely by feature flag(s)
• Yes, and covered partially by feature flag(s)
• No
• Not sure (briefly explain the situation below)

What level of testing was included in the change?

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• e2e
• integration
• unit

Which logical domain(s) does this change affect?

(for bug fixes/features, be as precise as possible. ex. Authentication, Annotation History, Review Stream etc.)

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[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +0.03% 🎉

Comparison is base (6523f96) 75.73% compared to head (bcd8147) 75.77%.
Report is 6 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4623      +/-   ##
===========================================
+ Coverage    75.73%   75.77%   +0.03%     
===========================================
  Files          157      157              
  Lines        12459    12458       -1     
===========================================
+ Hits          9436     9440       +4     
+ Misses        3023     3018       -5     

see 2 files with indirect coverage changes

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