Normalize remove_accents() data

[hakre]

The remove_accents() functions contains the translitaration data in diverse formats. To normalize the code, a format of arrays containing key=>value replacements where the string value of key transposes into the string value of value.

That's already common for a large part of the function.

[hakre]

latin-1, part I

[hakre]

latin-1, part II

[hakre]

One transliteration table for latin-1

[hakre]

get_transliteration_table()

[hakre]

Related: #16905