Merge bitcoin/bitcoin#23182: build: add python3.10 alias to AC_PATH_PROGS call in configure

ef15c574ff build: add python3.10 alias to AC_PATH_PROGS call in configure (fanquake)

Pull request description:

  Python 3.10 is [now released](https://pythoninsider.blogspot.com/2021/10/python-3100-is-available.html), and has been available as a beta/rc in distros for a little while already.

ACKs for top commit:
  MarcoFalke:
    cr ACK ef15c574ff
  laanwj:
    Code review ACK ef15c574ff
  hebasto:
    ACK ef15c574ff, I have reviewed the code and it looks OK, I agree it can be merged.

Tree-SHA512: 4d503d43dfbe210ac6180c63276d4ebe1aa39b0ada2a36c1292634f86603c385179b3034759441401a9ee5022f7687ccd5f3432be5c4e63f2eba7ddb76f5cbb9

configure.ac

@@ -107,7 +107,7 @@ AC_PATH_TOOL(GCOV, gcov)
 AC_PATH_TOOL(LLVM_COV, llvm-cov)
 AC_PATH_PROG(LCOV, lcov)
 dnl Python 3.6 is specified in .python-version and should be used if available, see doc/dependencies.md
-AC_PATH_PROGS([PYTHON], [python3.6 python3.7 python3.8 python3.9 python3 python])
+AC_PATH_PROGS([PYTHON], [python3.6 python3.7 python3.8 python3.9, python3.10, python3 python])
 AC_PATH_PROG(GENHTML, genhtml)
 AC_PATH_PROG([GIT], [git])
 AC_PATH_PROG(CCACHE,ccache)