create functional builder

[wazazaby]

benchstat results against the standard "builder pattern" builder.

goos: darwin
goarch: arm64
pkg: github.com/wazazaby/vimebu
                                                          │ builder.txt │              func.txt               │
                                                          │   sec/op    │   sec/op     vs base                │
BuilderTestCases/metric_with_labels-10                      68.60n ± 0%   64.37n ± 3%   -6.17% (p=0.000 n=15)
BuilderTestCases/metric_with_single_label-10                49.33n ± 0%   46.44n ± 0%   -5.86% (p=0.000 n=15)
BuilderTestCases/metric_without_label-10                    34.98n ± 0%   22.19n ± 0%  -36.56% (p=0.000 n=15)
BuilderTestCases/some_empty_labels_and_values-10            57.57n ± 1%   51.93n ± 0%   -9.80% (p=0.000 n=15)
BuilderTestCases/values_contain_double_quotes-10            473.9n ± 1%   470.7n ± 1%        ~ (p=0.076 n=15)
BuilderTestCases/values_with_and_without_double_quotes-10   509.1n ± 1%   504.0n ± 1%   -1.00% (p=0.001 n=15)
geomean                                                     108.6n        96.69n       -11.00%

                                                          │ builder.txt │              func.txt               │
                                                          │    B/op     │    B/op     vs base                 │
BuilderTestCases/metric_with_labels-10                       64.00 ± 0%   64.00 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/metric_with_single_label-10                 32.00 ± 0%   32.00 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/metric_without_label-10                     32.00 ± 0%   32.00 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/some_empty_labels_and_values-10             48.00 ± 0%   48.00 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/values_contain_double_quotes-10             112.0 ± 0%   112.0 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/values_with_and_without_double_quotes-10    160.0 ± 0%   160.0 ± 0%       ~ (p=1.000 n=15) ¹
geomean                                                      61.92        61.92       +0.00%
¹ all samples are equal

                                                          │ builder.txt │              func.txt               │
                                                          │  allocs/op  │ allocs/op   vs base                 │
BuilderTestCases/metric_with_labels-10                       1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/metric_with_single_label-10                 1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/metric_without_label-10                     1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/some_empty_labels_and_values-10             1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/values_contain_double_quotes-10             1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=15) ¹
BuilderTestCases/values_with_and_without_double_quotes-10    1.000 ± 0%   1.000 ± 0%       ~ (p=1.000 n=15) ¹
geomean                                                      1.000        1.000       +0.00%
¹ all samples are equal