Add getCacheKey() and getCacheTag() to AbstractPdoSchema

[Tigrov]

Move the methods from concrete drivers to AbstractPdoSchema class.

Related PRs

• Remove getCacheKey() and getCacheTag() from Schema db-sqlite#347
• Remove getCacheKey() and getCacheTag() from Schema db-mysql#386
• Remove getCacheKey() and getCacheTag() from Schema db-pgsql#396
• Remove getCacheKey() and getCacheTag() from Schema db-mssql#352
• Remove getCacheKey() and getCacheTag() from Schema db-oracle#315

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Fixed issues

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.23%. Comparing base (f99c144) to head (cc76701).

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #943   +/-   ##
=========================================
  Coverage     99.23%   99.23%           
- Complexity     1532     1534    +2     
=========================================
  Files            98       98           
  Lines          3811     3815    +4     
=========================================
+ Hits           3782     3786    +4     
  Misses           29       29           

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