Remove `--configPath` CLI option in the next major release

[vicb]

--configPath has been deprecated in #862.

Keeping this issue around until we drop it in 2.x

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As of 1.7 all of --configPath, --config, and --c CLI args can be used to set the wrangler config path.

--configPath is not in line with what wrangler uses (--config, --c) and should eventually be removed.

Proposal on how to get there:

• rename the configPath arg to config with a single c alias
• add a "new" arg configPath (w/o alias)

The new behavior would be:

• error early when both config and configPath flags are set
• use either config or configPath when only one of them is set
• print a deprecation warning when configPath is used
• remove the deprecated configPath in the next major release