Migrate logging implementation

[alexandernorth]

In order to help with observability, this PR migrates the existing logging framework to a logr.Logger based one, which is passed to various functions through the context.
This has the advantage that fields can be added to the logger as the application proceeds, adding relevant context to the log output and grouping together messages which belong to the same request/goroutine/...
It is also using structured logging which can help when integrating logs into observability tools.

This also refactors the netconf set function to have only one version of the code to handle setting to running or candidate stores, rather than two separate functions

[codecov]

Codecov Report

❌ Patch coverage is 7.50469% with 493 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pkg/server/schema.go	0.00%	94 Missing ⚠️
pkg/server/datastore.go	0.00%	50 Missing ⚠️
pkg/server/server.go	0.00%	48 Missing ⚠️
pkg/datastore/target/nc.go	9.61%	47 Missing ⚠️
pkg/datastore/datastore_rpc.go	0.00%	46 Missing ⚠️
pkg/datastore/transaction_rpc.go	0.00%	37 Missing ⚠️
pkg/server/transaction.go	0.00%	32 Missing ⚠️
pkg/utils/leaf_convert.go	0.00%	20 Missing ⚠️
pkg/datastore/target/gnmi.go	0.00%	18 Missing ⚠️
pkg/server/intent.go	0.00%	16 Missing ⚠️
... and 20 more

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