Speed up processor initialization

[milseman]

Moves register initialization to the program where it can be done once. Speeds
up use cases where the same regex is applied to many small inputs.

[milseman]

Perf improvements on top of #787

Comparing against saved benchmark result before_me_registers
=== Regressions ======================================================================
- DiceRollsInText_All                     28.8ms	28.5ms	255µs		0.9%
- DiceRollsInText_All_Scalar              27.2ms	27ms	161µs		0.6%
- LiteralSearchNotFound_All_Scalar        1.71ms	1.62ms	85.9µs		5.3%
- LiteralSearch_All                       2.65ms	2.58ms	76.6µs		3.0%
- LiteralSearch_All_Scalar                1.71ms	1.66ms	51.5µs		3.1%
=== Improvements =====================================================================
- CompilerMessages_All_Scalar             74.6ms	77.3ms	-2.68ms		-3.5%
- CompilerMessages_All                    83.8ms	85ms	-1.25ms		-1.5%
- EmojiRegex_All                          75.6ms	76.7ms	-1.03ms		-1.3%
- InvertedCCC_All                         5.73ms	6.72ms	-986µs		-14.7%
- EmailLookaheadNoMatches_All_Scalar      18.4ms	19.3ms	-904µs		-4.7%
- InvertedCCC_All_Scalar                  5.69ms	6.54ms	-842µs		-12.9%
- DiceNotation                            3.59ms	4.37ms	-780µs		-17.9%
- DiceNotation_Scalar                     3.46ms	4.22ms	-757µs		-17.9%
- FSPathsRegexFound_Scalar                2.99ms	3.7ms	-711µs		-19.2%
- FSPathsRegex                            3.35ms	4.05ms	-698µs		-17.2%
- FSPathsRegex_Scalar                     3.25ms	3.93ms	-675µs		-17.2%
- FSPathsRegexFound                       3.07ms	3.74ms	-674µs		-18.0%
- FSPathsRegexNotFound                    3.09ms	3.73ms	-643µs		-17.2%
- EmailLookaheadList                      3.5ms	4.14ms	-640µs		-15.5%
- EmailLookaheadList_Scalar               3.38ms	4.02ms	-636µs		-15.8%
- FSPathsRegexNotFound_Scalar             3ms	3.6ms	-605µs		-16.8%
- MACAddress                              1.88ms	2.41ms	-526µs		-21.9%
- IPv4Address                             1.57ms	2.08ms	-513µs		-24.7%
- IPv4Address_Scalar                      1.5ms	2ms	-504µs		-25.2%
- IPv6Address                             1.94ms	2.44ms	-501µs		-20.5%
- MACAddress_Scalar                       1.84ms	2.34ms	-500µs		-21.4%
- IPv6Address_Scalar                      1.82ms	2.32ms	-492µs		-21.2%
- EmailRFCNoMatches_All_Scalar            43.2ms	43.7ms	-470µs		-1.1%
- EmailRFCNoMatches_All                   45.3ms	45.8ms	-463µs		-1.0%
- EmailLookaheadNoMatches_All             20.1ms	20.5ms	-440µs		-2.1%
- EmailRFC_All_Scalar                     30.4ms	30.8ms	-415µs		-1.3%
- EmailRFC_All                            31ms	31.3ms	-318µs		-1.0%
- symDiffCCC_All                          16.1ms	16.4ms	-298µs		-1.8%
- SubtractionCCC_All_Scalar               5.47ms	5.73ms	-260µs		-4.5%
- SubtractionCCC_All                      5.47ms	5.73ms	-253µs		-4.4%
- Words_All                               4.64ms	4.88ms	-243µs		-5.0%
- BasicBuiltinCharacterClass_All_Scalar   2.39ms	2.61ms	-227µs		-8.7%
- symDiffCCC_All_Scalar                   16.2ms	16.4ms	-206µs		-1.3%
- AnchoredNotFound_All_Scalar             5.7ms	5.88ms	-183µs		-3.1%
- EmailBuiltinCharacterClass_All_Scalar   8.71ms	8.9ms	-182µs		-2.0%
- Words_All_Scalar                        4.54ms	4.71ms	-165µs		-3.5%
- ReluctantQuantWithTerminal_Whole_Scalar 5.68ms	5.82ms	-147µs		-2.5%
- BasicRangeCCC_All                       2.97ms	3.11ms	-144µs		-4.6%
- EmailBuiltinCharacterClass_All          8.85ms	8.98ms	-130µs		-1.4%
- AnchoredNotFound_First                  7.94ms	8.07ms	-125µs		-1.6%
- AnchoredNotFound_All                    7.94ms	8.07ms	-121µs		-1.5%
- BasicRangeCCC_All_Scalar                2.97ms	3.09ms	-121µs		-3.9%
- ReluctantQuantWithTerminal_Whole        5.71ms	5.83ms	-115µs		-2.0%
- ReluctantQuant_Whole                    3.37ms	3.48ms	-112µs		-3.2%
- ReluctantQuant_Whole_Scalar             3.37ms	3.48ms	-112µs		-3.2%
- EmailLookahead_All_Scalar               17.5ms	17.6ms	-106µs		-0.6%
- BasicCCC_All                            2.84ms	2.94ms	-106µs		-3.6%
- BasicCCC_All_Scalar                     2.84ms	2.94ms	-98.5µs		-3.4%
- CaseInsensitiveCCC_All_Scalar           3.17ms	3.27ms	-95.4µs		-2.9%
- CaseInsensitiveCCC_All                  3.17ms	3.27ms	-94.1µs		-2.9%
- EmailLookahead_All                      18.6ms	18.7ms	-82.1µs		-0.4%
- HangulSyllable_All                      2.6ms	2.67ms	-74µs		-2.8%
- HangulSyllable_All_Scalar               1.88ms	1.95ms	-72.3µs		-3.7%
- Numbers_All_Scalar                      2.04ms	2.11ms	-72µs		-3.4%
- IntersectionCCC_All                     5.09ms	5.15ms	-64.3µs		-1.2%
- Lines_All_Scalar                        763µs	823µs	-60.2µs		-7.3%
- GraphemeBreakNoCap_All                  1.58ms	1.64ms	-54.2µs		-3.3%
- GraphemeBreakNoCap_All_Scalar           1.52ms	1.57ms	-54µs		-3.4%
- BasicBuiltinCharacterClass_All          3.04ms	3.09ms	-45.4µs		-1.5%
- Lines_All                               806µs	847µs	-41.3µs		-4.9%
- Numbers_All                             2.55ms	2.57ms	-19.1µs		-0.7%
- Css_All_Scalar                          2.07ms	2.09ms	-19.1µs		-0.9%
- IntersectionCCC_All_Scalar              5.08ms	5.1ms	-16.8µs		-0.3%
- Css_All                                 2.31ms	2.32ms	-14.9µs		-0.6%
- URLWithWordBoundaries_All               1.75ms	1.76ms	-11.7µs		-0.7%
- URLWithWordBoundaries_All_SimpleWordBoundaries 555µs	558µs	-3.33µs		-0.6%

[milseman]

(Part of this speedup is we happen to now hit a happy path where a lot of the ARC gets eliminated.)

[milseman]

@swift-ci please test

[milseman]

@swift-ci please test