Announce on which DB migration is run

What does this MR do and why?

This improves migration output to:

• prefix migration output with indicator of database on which it runs
• makes skipped migrations to also include announcements (migrating/migrated) with version and name

Resolves:

• #336765 (closed)

Related to:

• !86525 (comment 951725004)

Output

$ bin/rake db:migrate
main: == 20220516123101 AddTextLimitToGloballyAllowedIpsOnApplicationSettings: migrating 
main: -- transaction_open?()
main:    -> 0.0000s
main: -- current_schema()
main:    -> 0.0010s
main: -- transaction_open?()
main:    -> 0.0000s
main: -- execute("ALTER TABLE application_settings\nADD CONSTRAINT check_734cc9407a\nCHECK ( char_length(globally_allowed_ips) <= 255 )\nNOT VALID;\n")
main:    -> 0.0028s
main: -- current_schema()
main:    -> 0.0005s
main: -- execute("ALTER TABLE application_settings VALIDATE CONSTRAINT check_734cc9407a;")
main:    -> 0.0011s
main: == 20220516123101 AddTextLimitToGloballyAllowedIpsOnApplicationSettings: migrated (0.0145s) 

main: == 20220517144749 RemoveVulnerabilityApprovalRules: migrating ===============
main: -- The migration is skipped since it modifies the [:gitlab_main].
main: -- This database can only apply migrations in one of the following schemas: [:gitlab_ci, :gitlab_shared].
main: == 20220517144749 RemoveVulnerabilityApprovalRules: migrated (0.0001s) ====== 

MR acceptance checklist

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