Fewer wire allocs in SQL() implementations

[max-hoffman]

Optimizes SQL() implementations that convert interface values into type-specific byte arrays. Combination of skipping runtime.convT checks, that unnecessarily allocated variables to the heap, redundant byte array copying, and other conversion inefficiencies.

dolt perf here: dolthub/dolt#8651

goos: darwin
goarch: arm64
pkg: github.com/dolthub/go-mysql-server/sql/types
cpu: Apple M3 Pro
                │  before.txt  │             after.txt              │
                │    sec/op    │   sec/op     vs base               │
NumI64SQL-12       62.04n ± 2%   51.13n ± 1%  -17.59% (p=0.002 n=6)
Varchar10SQL-12    66.85n ± 1%   31.38n ± 2%  -53.06% (p=0.002 n=6)
TimespanSQL-12     62.36n ± 0%   40.31n ± 1%  -35.35% (p=0.002 n=6)
TimestampSQL-12   1960.0n ± 1%   255.0n ± 2%  -86.99% (p=0.002 n=6)
DatetimeSQL-12    1968.5n ± 0%   269.5n ± 3%  -86.31% (p=0.002 n=6)
EnumSQL-12        111.85n ± 1%   37.49n ± 1%  -66.48% (p=0.002 n=6)
SetSQL-12         175.15n ± 0%   63.55n ± 1%  -63.72% (p=0.002 n=6)
BitSQL-12          41.84n ± 1%   41.74n ± 1%        ~ (p=0.589 n=6)
DecimalSQL-12      683.8n ± 3%   281.9n ± 1%  -58.77% (p=0.002 n=6)
NumF64SQL-12      105.15n ± 1%   91.72n ± 0%  -12.77% (p=0.002 n=6)
geomean            189.2n        80.50n       -57.45%

                │  before.txt  │              after.txt              │
                │     B/op     │    B/op     vs base                 │
NumI64SQL-12        24.00 ± 0%   16.00 ± 0%  -33.33% (p=0.002 n=6)
Varchar10SQL-12    40.000 ± 0%   8.000 ± 0%  -80.00% (p=0.002 n=6)
TimespanSQL-12      24.00 ± 0%   16.00 ± 0%  -33.33% (p=0.002 n=6)
TimestampSQL-12   1520.00 ± 0%   56.00 ± 0%  -96.32% (p=0.002 n=6)
DatetimeSQL-12    1520.00 ± 0%   56.00 ± 0%  -96.32% (p=0.002 n=6)
EnumSQL-12        112.000 ± 0%   8.000 ± 0%  -92.86% (p=0.002 n=6)
SetSQL-12          136.00 ± 0%   16.00 ± 0%  -88.24% (p=0.002 n=6)
BitSQL-12           16.00 ± 0%   16.00 ± 0%        ~ (p=1.000 n=6) ¹
DecimalSQL-12       439.0 ± 0%   228.0 ± 0%  -48.06% (p=0.002 n=6)
NumF64SQL-12        38.00 ± 0%   31.00 ± 0%  -18.42% (p=0.002 n=6)
geomean             108.0        24.94       -76.92%
¹ all samples are equal

                │ before.txt  │              after.txt              │
                │  allocs/op  │ allocs/op   vs base                 │
NumI64SQL-12       2.000 ± 0%   1.000 ± 0%  -50.00% (p=0.002 n=6)
Varchar10SQL-12    2.000 ± 0%   1.000 ± 0%  -50.00% (p=0.002 n=6)
TimespanSQL-12     2.000 ± 0%   1.000 ± 0%  -50.00% (p=0.002 n=6)
TimestampSQL-12   42.000 ± 0%   3.000 ± 0%  -92.86% (p=0.002 n=6)
DatetimeSQL-12    42.000 ± 0%   3.000 ± 0%  -92.86% (p=0.002 n=6)
EnumSQL-12         3.000 ± 0%   1.000 ± 0%  -66.67% (p=0.002 n=6)
SetSQL-12          5.000 ± 0%   2.000 ± 0%  -60.00% (p=0.002 n=6)
BitSQL-12          2.000 ± 0%   2.000 ± 0%        ~ (p=1.000 n=6) ¹
DecimalSQL-12      22.00 ± 0%   10.00 ± 0%  -54.55% (p=0.002 n=6)
NumF64SQL-12       3.000 ± 0%   2.000 ± 0%  -33.33% (p=0.002 n=6)
geomean            5.554        1.931       -65.24%
¹ all samples are equal

[zachmu]

LGTM