python -m base64 do not handle stdin correct like ast.py or json.tool

[yihong0618]

Bug report

Bug description:

➜  cpython git:(hy/handle_base64_sysin) ./python.exe -m base64
hello world
^D # type ctrl+D
# nothing happen need to ctrl+d three times

for -m ast or -m json it handle stdin input with ctrl+d right

➜  cpython git:(hy/handle_base64_sysin) ./python.exe -m json  
1234 
1234 # ctrl +d

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-138775: fix handle python -m base64 stdin correct with EOF signal #138776