Reduce allocations when generating sequences

[dirkschumacher]

An experiment to reduce allocations

name                                       old time/op    new time/op    delta
pkg:github.com/nextmv-io/nextroute goos:darwin goarch:arm64
SequenceGeneratorSequence-8                  1.62µs ± 1%    1.65µs ± 1%   +1.94%  (p=0.000 n=9+9)
SequenceGenerator3-8                         14.8µs ± 2%    11.8µs ± 1%  -20.03%  (p=0.000 n=10+10)
pkg:github.com/nextmv-io/nextroute/tests/golden goos:darwin goarch:arm64
Golden/testdata/complex_precedence.json-8   24.0ms ±101%   32.3ms ±108%     ~     (p=0.315 n=10+10)

name                                       old alloc/op   new alloc/op   delta
pkg:github.com/nextmv-io/nextroute goos:darwin goarch:arm64
SequenceGeneratorSequence-8                    467B ± 2%      454B ± 0%   -2.88%  (p=0.000 n=9+9)
SequenceGenerator3-8                         6.27kB ± 1%    5.01kB ± 1%  -20.01%  (p=0.000 n=10+10)
pkg:github.com/nextmv-io/nextroute/tests/golden goos:darwin goarch:arm64
Golden/testdata/complex_precedence.json-8    3.50MB ±92%    4.05MB ±91%     ~     (p=0.529 n=10+10)

name                                       old allocs/op  new allocs/op  delta
pkg:github.com/nextmv-io/nextroute goos:darwin goarch:arm64
SequenceGeneratorSequence-8                    10.0 ± 0%       9.0 ± 0%  -10.00%  (p=0.000 n=10+10)
SequenceGenerator3-8                           71.0 ± 0%      31.0 ± 0%  -56.34%  (p=0.000 n=10+10)
pkg:github.com/nextmv-io/nextroute/tests/golden goos:darwin goarch:arm64
Golden/testdata/complex_precedence.json-8     42.4k ±93%     44.1k ±92%     ~     (p=0.853 n=10+10)