RFR: 8333685: Make update-copyright-year script more useful

[Sonia Zaldana Calles]

Hi all, 

This PR addresses [8333685](https://bugs.openjdk.org/browse/JDK-8333685). 

I have added the following enhancements: 
- Removed uses of `fgrep` and `egrep` with `grep -F` and `grep -E` respectively. 
- Altered default behaviour to limit the processed changesets to those in the current branch and the current year. 
- Enabled an option to modify all changesets in the year if desired (this was the previous default behaviour). 
- Added named parameters and enabled `--help`.
- Removed mercurial support. 
- Fixed a bug where copyright headers that didn't have a comma following the initial year of creation were not getting picked up. For example, [here](https://github.com/openjdk/jdk/blob/512b2b4f141f9a202984150b0427372e1a409a50/src/hotspot/cpu/zero/copy_zero.hpp#L3). 
- Fixed a bug where copyright headers missing the copyright symbol (c) were not getting picked up. Refer to the example above as well. 

Thanks, 
Sonia

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Commit messages:
 - Support for copyright statements missing symbol
 - 8333685: Make update-copyright-year script more useful

Changes: https://git.openjdk.org/jdk/pull/19605/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19605&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333685
  Stats: 97 lines in 1 file changed: 38 ins; 26 del; 33 mod
  Patch: https://git.openjdk.org/jdk/pull/19605.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19605/head:pull/19605

PR: https://git.openjdk.org/jdk/pull/19605