add Server configuration WOODPECKER_DATABASE_MAX_CONNECTIONS

[sinlov]

Clear and concise description of the problem

woodpecker ci record jobs is slow, can change database max connections to improve?

Suggested solution

woodpecker use xorm.io for datastore engine

can use connections-pool, and support

• engine.SetMaxIdleConns()
• engine.SetMaxOpenConns()

let Server configuration add flag WOODPECKER_DATABASE_MAX_CONNECTIONS to support

Alternative

No response

Additional context

No response

Validations

• Checked that the feature isn't part of the next version already [https://woodpecker-ci.org/faq#which-version-of-woodpecker-should-i-use]
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[qwerty287]

Will be available in next version

#4212