MeterFilters configured after a Meter has been registered

[shakuzen]

In #4917 we took a step toward warning users about this situation with the following log message:

A MeterFilter is being configured after a Meter has been registered to this registry.

Historically, we have allowed configuring MeterFilters after meters have been registered. Depending on how meters are used, the negative effects of doing this can be minimal. It is ideal to configure all desired MeterFilters before registering any Meters so that all registered Meters will have all configured MeterFilters applied.

If users have a use case for configuring MeterFilters "late" (after a Meter has been registered), we would be interested in understanding that so we can make informed decisions about what we allow in the future. It may also be the case that something out of a user's direct control is causing this situation to happen - a framework or library the user is using may be configuring MeterFilters or registering Meters at timing not controlled by the user. We would like to hear about these cases so we can work with the libraries or frameworks. The above log message includes a stack trace when DEBUG level logging is enabled on the meter registry implementation in question. This stack trace will help track down what is configuring the MeterFilter late.