[decimal] Implement the log() and the log10() functions

[forfudan]

This pull request includes the log and log10 functions in the decimojo library.
It also introduces a new benchmark for the log10 function and includes several updates to the Decimal struct in the decimojo library.

Library Updates:

• Included log and log10 in the decimojo library's __init__.mojo file to make them available for import.

New Benchmark for log10 Function:

• Added a comprehensive benchmark for the log10 function in benches/bench_log10.mojo to compare performance against Python's decimal module with diverse test cases.

Project Configuration Updates:

• Updated benches/bench.mojo to include bench_log10 in the list of benchmarks.
• Updated mojoproject.toml to include test_log and test_log10 in the test configurations and bench_log10 in the benchmark configurations.

Decimal Struct Enhancements:

• Added @always_inline decorator to several static methods and instance methods in struct Decimal to improve performance.