Add update mechanism for Terminfo, and common user-alias data (#53285)

Now that we take care of terminfo parsing ourselves, having a clear
origin and processing method for arriving at our reference terminfo data
seems somewhat important.

The original form was acquired by re-purposing some pre-processed
terminfo data from NCurses (I forget the exact source). I considered
adding a separate ingestion/processing script, but it occurred to me
that it would make sense to have the method for updating the data file
be _in_ the data file, by turning it into a quine.

This seems to work rather well, and so long as the NCurses source file
format stays the same, updating the terminfo data is now dead simple.

While working on the terminfo files, some minor refactors popped up as
"probably nice to have". One of which makes the reported number of
flags/numbers/strings actually accurate.

Lastly, to support the ergonomic use of capability variable names
instead of the short (read: uninformative) capname, we now also import
the NCurses-recognised extended capabilities, and generate/specify some
nice aliases for them.

-----

If we separate out the terminfo parser/data into a small stdlib, the
state here will be the initial state of the repo.

base/terminfo.jl

@@ -66,9 +66,10 @@ struct TermInfo
     numbers::Dict{Symbol, Int}
     strings::Dict{Symbol, String}
     extensions::Union{Nothing, Set{Symbol}}
+    aliases::Dict{Symbol, Symbol}
 end
 
-TermInfo() = TermInfo([], Dict(), Dict(), Dict(), nothing)
+TermInfo() = TermInfo([], Dict(), Dict(), Dict(), nothing, Dict())
 
 function read(data::IO, ::Type{TermInfoRaw})
     # Parse according to `term(5)`
@@ -175,24 +176,28 @@ function TermInfo(raw::TermInfoRaw)
     flags = Dict{Symbol, Bool}()
     numbers = Dict{Symbol, Int}()
     strings = Dict{Symbol, String}()
+    aliases = Dict{Symbol, Symbol}()
     extensions = nothing
     for (flag, value) in zip(TERM_FLAGS, raw.flags)
-        flags[flag.short] = value
-        flags[flag.long] = value
+        flags[flag.name] = value
+        aliases[flag.capname] = flag.name
     end
     for (num, value) in zip(TERM_NUMBERS, raw.numbers)
-        numbers[num.short] = Int(value)
-        numbers[num.long] = Int(value)
+        numbers[num.name] = Int(value)
+        aliases[num.capname] = num.name
     end
     for (str, value) in zip(TERM_STRINGS, raw.strings)
         if !isnothing(value)
-            strings[str.short] = value
-            strings[str.long] = value
+            strings[str.name] = value
+            aliases[str.capname] = str.name
         end
     end
     if !isnothing(raw.extended)
         extensions = Set{Symbol}()
-        for (key, value) in raw.extended
+        longalias(key, value) = first(get(TERM_USER, (typeof(value), key), (nothing, "")))
+        for (short, value) in raw.extended
+            long = longalias(short, value)
+            key = something(long, short)
             push!(extensions, key)
             if value isa Bool
                 flags[key] = value
@@ -201,26 +206,30 @@ function TermInfo(raw::TermInfoRaw)
             elseif value isa String
                 strings[key] = value
             end
+            if !isnothing(long)
+                aliases[short] = long
+            end
         end
     end
-    TermInfo(raw.names, flags, numbers, strings, extensions)
+    TermInfo(raw.names, flags, numbers, strings, extensions, aliases)
 end
 
-get(ti::TermInfo, key::Symbol, default::Bool) = get(ti.flags, key, default)
-get(ti::TermInfo, key::Symbol, default::Int) = get(ti.numbers, key, default)
-get(ti::TermInfo, key::Symbol, default::String) = get(ti.strings, key, default)
+get(ti::TermInfo, key::Symbol, default::Bool)   = get(ti.flags,   get(ti.aliases, key, key), default)
+get(ti::TermInfo, key::Symbol, default::Int)    = get(ti.numbers, get(ti.aliases, key, key), default)
+get(ti::TermInfo, key::Symbol, default::String) = get(ti.strings, get(ti.aliases, key, key), default)
 
 haskey(ti::TermInfo, key::Symbol) =
-    haskey(ti.flags, key) || haskey(ti.numbers, key) || haskey(ti.strings, key)
+    haskey(ti.flags, key) || haskey(ti.numbers, key) || haskey(ti.strings, key) || haskey(ti.aliases, key)
 
 function getindex(ti::TermInfo, key::Symbol)
     haskey(ti.flags, key) && return ti.flags[key]
     haskey(ti.numbers, key) && return ti.numbers[key]
     haskey(ti.strings, key) && return ti.strings[key]
+    haskey(ti.aliases, key) && return getindex(ti, ti.aliases[key])
     throw(KeyError(key))
 end
 
-keys(ti::TermInfo) = keys(ti.flags) ∪ keys(ti.numbers) ∪ keys(ti.strings)
+keys(ti::TermInfo) = keys(ti.flags) ∪ keys(ti.numbers) ∪ keys(ti.strings) ∪ keys(ti.aliases)
 
 function show(io::IO, ::MIME"text/plain", ti::TermInfo)
     print(io, "TermInfo(", ti.names, "; ", length(ti.flags), " flags, ",