What does this PR do?

Upcoming Go 1.24 release introduces a new go vet check (golang/go#60529) for printf calls with non-const format and no args. This causes go test to fail to run in gotip:

❯ gotip test gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer
# gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer
# [gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer]
ddtrace/tracer/abandonedspans.go:276:11: non-constant format string in call to gopkg.in/DataDog/dd-trace-go.v1/internal/log.Warn
ddtrace/tracer/otel_dd_mappings.go:101:14: non-constant format string in call to gopkg.in/DataDog/dd-trace-go.v1/internal/log.Warn
ddtrace/tracer/slog.go:44:13: non-constant format string in call to gopkg.in/DataDog/dd-trace-go.v1/internal/log.Debug
ddtrace/tracer/slog.go:46:12: non-constant format string in call to gopkg.in/DataDog/dd-trace-go.v1/internal/log.Info
ddtrace/tracer/slog.go:48:12: non-constant format string in call to gopkg.in/DataDog/dd-trace-go.v1/internal/log.Warn
ddtrace/tracer/slog.go:50:13: non-constant format string in call to gopkg.in/DataDog/dd-trace-go.v1/internal/log.Error
ddtrace/tracer/option_test.go:341:13: non-constant format string in call to (*testing.common).Fatalf
FAIL    gopkg.in/DataDog/dd-trace-go.v1/ddtrace/tracer [build failed]
FAIL

We decided to strategically modify all logging statements, after trying refactoring internal/log API to offer:

• Debug, Info, Warn, Error functions for logging a string without arguments
• Debugf, Infof, Warnf, Errorf function for logging formatted messages with arguments

This caused a significant amount of changes across the repository, but we want to keep the API as coherent as possible. It mirrors stdlib's log API.

Motivation

Avoid unintended consequences from upcoming Go 1.24 release.

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.
• For internal contributors, a matching PR should be created to the v2-dev branch and reviewed by @DataDog/apm-go.

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