RFR: 8375646: Some parser flags seem unused [v3]

[Maurizio Cimadamore]

> Some of the flags in `JavacParser` are never set, such as `TYPEARGS` and `NOPARAMS`.
> 
> Another flag, namely `NODIAMOND` can easily be avoided by looking ahead one token.
> 
> This PR removes all the three flags. The main issue with these changes had to do with removing the `boolean allowDiamon` parameter from the `typeArguments` method, as doing so makes it clash with another similarly named method.
> For this reason, this PR distinguish between:
> 
> * `typeArguments` -- a method that parses a type argument list, returns a list of `JCExpression`s
> * `typeApply` -- a method that parses and applies type arguments to an existing type (a `JCExpression). This returns a new `JCExpression` (typically a `JCTypeApply`).

Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/29302/files
  - new: https://git.openjdk.org/jdk/pull/29302/files/01cfaf20..2cfc5de0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29302&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29302&range=01-02

  Stats: 6 lines in 1 file changed: 0 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/29302.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29302/head:pull/29302

PR: https://git.openjdk.org/jdk/pull/29302