Fix: Charset of `ACAutomationMatcherGroup` should accept all ASCII characters

[Vigilans]

In previous ac automation implementations, we thought a domain name would only contain valid characters (the LDH subset) (because DNS and http requests should validate the domain beforehand).

But actually this is not the case, and doing nslookup { <v2ray-dns> would cause ACAutomationMatcherGroup to fail because acCharset does not contain a index mapping for character { (whose code index is larger than z). This has caused a in-daily-use v2ray dns to crash.

Therefore, this PR changes acCharset to be 256 elements long, to be able to cover the whole range of a byte of character. All invalid characters are mapped to a reserved index 0.

[codecov-commenter]

Codecov Report

Base: 38.97% // Head: 38.85% // Decreases project coverage by -0.12% :warning:

Coverage data is based on head (f8ce89f) compared to base (305661c). Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1988      +/-   ##
==========================================
- Coverage   38.97%   38.85%   -0.13%     
==========================================
  Files         616      611       -5     
  Lines       36442    36367      -75     
==========================================
- Hits        14204    14129      -75     
  Misses      20652    20652              
  Partials     1586     1586              

Impacted Files	Coverage Δ
common/strmatcher/matchergroup_ac_automation.go	100.00% <ø> (ø)
app/proxyman/outbound/errors.generated.go	0.00% <0.00%> (-100.00%)	:arrow_down:
common/task/task.go	88.88% <0.00%> (-7.41%)	:arrow_down:
testing/servers/tcp/tcp.go	81.81% <0.00%> (-5.46%)	:arrow_down:
testing/scenarios/common.go	75.00% <0.00%> (-4.29%)	:arrow_down:
app/proxyman/outbound/handler.go	36.61% <0.00%> (-4.23%)	:arrow_down:
transport/internet/kcp/dialer.go	80.39% <0.00%> (-3.93%)	:arrow_down:
transport/internet/websocket/connection.go	16.51% <0.00%> (-3.67%)	:arrow_down:
transport/internet/kcp/connection.go	69.61% <0.00%> (-2.21%)	:arrow_down:
common/session/context.go	56.66% <0.00%> (-1.67%)	:arrow_down:
... and 8 more

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