runtime(sh): Do not conflate empty array and function declarations in Bash

runtime(sh): Do not conflate empty array and function declarations in Bash

Although the "=" character is permitted in function names,
a construct that parses as a variable assignment is
preferred to it parsing as a function declaration.  See the
updated test file "sh_functions_bash.sh" for details.

fixes:  #20183
closes: #20205

Co-authored-by: Doug Kearns <dougkearns@gmail.com>
Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>