Berry add global function format as a simpler syntax to string.format

[s-hadinger]

Description:

Berry: provide a global function format() as a simpler syntax for import string [...] string.format(). This remains backwards compatible.

As a side effect, performance should be slightly improved and code smaller.

Before:

def f(x)
    import string
    return string.format("x=%i", x)
end

# compiles to
  0000  IMPORT	R1	K0            # first lookup
  0001  GETMET	R2	R1	K1    # second lookup
  0002  LDCONST	R4	K2
  0003  MOVE	R5	R0
  0004  CALL	R2	3
  0005  RET	1	R2

After:

def f(x)
    return format("x=%i", x)
end

# compiles to
  0000  GETGBL	R1	G24            # no lookup, simple indexed access
  0001  LDCONST	R2	K0
  0002  MOVE	R3	R0
  0003  CALL	R1	2
  0004  RET	1	R1

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.4.9
• The code change is tested and works with Tasmota core ESP32 V.2.0.10
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass