Don't send sys.argv[0] as program_name to MySQL server by default

[Nothing4You]

What do these changes do?

This ports PyMySQL's change: PyMySQL/PyMySQL#755

Are there changes in behavior for the user?

We no longer implicitly send sys.argv[0] to the DB server by default.
For the majority of users this should not be relevant, if you need this value you can still pass it explicitly.

Related issue number

fixes #620, closes #621

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• Add a new news fragment to CHANGES.txt

[codecov]

Codecov Report

Merging #681 (54865b2) into master (c1c2fb5) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #681      +/-   ##
==========================================
+ Coverage   83.56%   83.60%   +0.03%     
==========================================
  Files          12       12              
  Lines        2051     2049       -2     
  Branches      332      331       -1     
==========================================
- Hits         1714     1713       -1     
  Misses        266      266              
+ Partials       71       70       -1     

Flag	Coverage Δ
ubuntu-latest_3.7_mariadb-10.2	82.31% <ø> (+0.03%)	⬆️
ubuntu-latest_3.7_mariadb-10.3	82.31% <ø> (+0.03%)	⬆️
ubuntu-latest_3.7_mariadb-10.4	82.31% <ø> (+0.03%)	⬆️
ubuntu-latest_3.7_mariadb-10.5	82.31% <ø> (+0.03%)	⬆️
ubuntu-latest_3.7_mariadb-10.6	82.31% <ø> (+0.03%)	⬆️
ubuntu-latest_3.7_mariadb-10.7	82.31% <ø> (+0.03%)	⬆️
ubuntu-latest_3.7_mysql-5.7	83.21% <ø> (+0.03%)	⬆️
ubuntu-latest_3.8_mariadb-10.2	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.8_mariadb-10.3	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.8_mariadb-10.4	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.8_mariadb-10.5	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.8_mariadb-10.6	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.8_mariadb-10.7	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.8_mysql-5.7	83.60% <ø> (+0.03%)	⬆️
ubuntu-latest_3.9_mariadb-10.2	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.9_mariadb-10.3	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.9_mariadb-10.4	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.9_mariadb-10.5	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.9_mariadb-10.6	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.9_mariadb-10.7	82.72% <ø> (+0.03%)	⬆️
ubuntu-latest_3.9_mysql-5.7	83.60% <ø> (+0.03%)	⬆️

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Impacted Files	Coverage Δ
aiomysql/connection.py	77.35% <ø> (+0.06%)	⬆️

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