Use consistent wording for referencing component

[h2oche]

When referencing the components of the records, some phrases use

1. Set the LexicalEnvironment of _calleeContext_ to _localEnv_.
1.  Let _env_ be the LexicalEnvironment of the running execution context.
1. Let _generator_ be the Generator component of _genContext_

and some phrases use

1. Set the running execution context's LexicalEnvironment to _blockEnv_.
1. Let _oldEnv_ be the running execution context's LexicalEnvironment.

I'm not sure which form is better to use, but I think it'd better to consistify those phrases.

[jmdyck]

When referencing the components of the records, ...

Note that execution contexts are not currently modelled as records. PR #2246 fixes that, and uses consistent phrasing to refer to their fields.