Add implementation of XPath function fn:tokenize (for formula linkbase to use)

[strr]

Reason for change

Arelle is missing support for some XPath 2.0 standard functions and there is a good chance that an upcoming taxonomy might use fn:tokenize() so add an implementation of it.

Description of change

Implement fn:tokenize() and add a few tests for it.

Steps to Test

A simple formula linkbase making use of tokenize (zipped purely to get past Github upload filter,)
test-tokenize-formula.zip

python arelleCmdLine.py -v -f test-tokenize-formula.xml

Without this pull request it fails:

[info] loaded in 0.03 secs at 2024-07-11T11:48:35 - C:\b\test-tokenize-formula.xml
[] Formula xpath2 grammar initialized in 0.63 secs -
[err:XPST0017] Variable set AssertionTokenizeAndJoin
Exception: Function named fn:tokenize does not have a custom or built-in implementation. - test-tokenize-formula.xml 14
[err:XPST0017] Variable set AssertionCountTokensZeroMatch
Exception: Function named fn:tokenize does not have a custom or built-in implementation. - test-tokenize-formula.xml 11
[err:XPST0017] Variable set AssertionCountTokens
Exception: Function named fn:tokenize does not have a custom or built-in implementation. - test-tokenize-formula.xml 8
[info] validated in 0.66 secs - C:\b\test-tokenize-formula.xml

With this pull request it succeeds:

[info] loaded in 0.03 secs at 2024-07-11T11:53:45 - C:\b\test-tokenize-formula.xml
[] Formula xpath2 grammar initialized in 1.01 secs -
[message:AssertionTokenizeAndJoin] Turn '  a b  c   ' into 'abc' 'abc'  - test-tokenize-formula.xml 14
[message:AssertionCountTokens] Length of count(fn:tokenize('a-b-c-d-e-f-g', '-')) should be 7 and actually is '7'  - test-tokenize-formula.xml 8
[message:AssertionCountTokensZeroMatch] Length of count(fn:tokenize('a-b-c-d-e-f-g-', '-')) should be 8 and actually is '8'  - test-tokenize-formula.xml 11
[info] validated in 1.05 secs - C:\b\test-tokenize-formula.xml

Alternately, the unit tests can be run:

pytest .\tests\unit_tests\arelle\test_functionfn.py

review:
@Arelle/arelle