fix: Optimize decimal creation macros

[kazuyukitanimura]

Which issue does this PR close?

Part of #679 and #670

Rationale for this change

This PR improves decimal creation macros

What changes are included in this PR?

Consolidated make_plain_decimal_impl to make_int_decimal_variant_impl

How are these changes tested?

Existing tests

[kazuyukitanimura]

OpenJDK 64-Bit Server VM 17.0.11+9-LTS on Mac OS X 14.5
Apple M1 Max
TPCDS Micro Benchmarks:                   Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
------------------------------------------------------------------------------------------------------------------------
q44                                                2156           2293         157        133.7           7.5       1.0X
q44: Comet (Scan)                                  1968           2068         102        146.5           6.8       1.1X
q44: Comet (Scan, Exec)                            2264           2343          50        127.3           7.9       1.0

[kazuyukitanimura]

Before

After

[kazuyukitanimura]

@andygrove @comphead @huaxingao @parthchandra @viirya

[andygrove]

👍

Consolidating the macros makes sense to me. Thanks @kazuyukitanimura.

[parthchandra]

Nice