feat: delete db dump comments by default

[sweatybridge]

What kind of change does this PR introduce?

fixes #1047

What is the current behavior?

• a lot of unnecessary comments generated from pg_dump
• unclear how to increase scanner buffer size

What is the new behavior?

• removes commented out lines from db dump by default
• adds db dump --keep-comments flag to maintain existing behaviour
• uses file length as the max buffer size by default
• prints help text when input token is longer than scanner buffer size

$ supabase db reset
...
bufio.Scanner: token too long
After statement 1:      BEGIN;
Try setting SUPABASE_SCANNER_BUFFER_SIZE=5MB (default is 256KB)

Additional context

Add any other context or screenshots.

[coveralls]

Pull Request Test Coverage Report for Build 4875173064

• 69 of 71 (97.18%) changed or added relevant lines in 7 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.1%) to 60.645%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/db.go	1	2	50.0%
internal/db/remote/commit/commit.go	0	1	0.0%

Files with Coverage Reduction	New Missed Lines	%
internal/testing/pgtest/mock.go	1	90.96%

Totals
Change from base Build 4870405574:	0.1%
Covered Lines:	4327
Relevant Lines:	7135

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💛 - Coveralls