Support scientific notation representation in PPL

[LantaoJin]

Description

Numbers of scientific notation can be recognized in SQL, but not in PPL. With this PR, numbers of scientific notation can be identified as double in PPL as same as in SQL.
Here are valid examples of scientific notation representations: 9e1, +9e+1, 900e-1, 9.0e1, 9.0e+1, 9.0E1, .9e+2, 0.09e+3, 900.0e-1, -900.0E-1.

• Example query:

POST /_plugins/_ppl
{
  "query": """
  search source=t | eval `9e1`=9e1 | fields `9e1`
  """
}

• Result without this PR:

SyntaxCheckException: Failed to parse query due to offending symbol [e1] at: ... | eval 9e1=9e1' <--- HERE`

• Result with this PR:

{
  "schema": [
    {
      "name": "9e1",
      "type": "double"
    }
  ],
  "datarows": [
    [
      90
    ]
  ]
}

Issues Resolved

Resolves #2826

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

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[dai-chen]

Thanks for the changes!

[LantaoJin]

Gently ping @penghuo @vamsi-amazon @YANG-DB