Add dast_submit_field to DAST site profile

Adds auth_submit_field of type text to dast_site_profiles. Adds model validations.

Add option to set DAST_SUBMIT_FIELD for on-demand DAST scans. Add ability to set Login to submit element.

Query: No new query is introduced.

Migration:

== 20220331174026 AddSubmitFieldToDastSiteProfiles: migrating =================
-- add_column(:dast_site_profiles, :auth_submit_field, :text)
   -> 0.0045s
== 20220331174026 AddSubmitFieldToDastSiteProfiles: migrated (0.0046s) ========

== 20220331174459 AddTextLimitToSubmitFieldDastSiteProfiles: migrating ========
-- transaction_open?()
   -> 0.0000s
-- current_schema()
   -> 0.0004s
-- transaction_open?()
   -> 0.0000s
-- execute("ALTER TABLE dast_site_profiles\nADD CONSTRAINT check_af44f54c96\nCHECK ( char_length(auth_submit_field) <= 255 )\nNOT VALID;\n")
   -> 0.0021s
-- current_schema()
   -> 0.0003s
-- execute("SET statement_timeout TO 0")
   -> 0.0011s
-- execute("ALTER TABLE dast_site_profiles VALIDATE CONSTRAINT check_af44f54c96;")
   -> 0.0024s
-- execute("RESET statement_timeout")
   -> 0.0013s
== 20220331174459 AddTextLimitToSubmitFieldDastSiteProfiles: migrated (0.0278s)

Rollback:

== 20220331174459 AddTextLimitToSubmitFieldDastSiteProfiles: reverting ========
-- transaction_open?()
   -> 0.0000s
-- transaction_open?()
   -> 0.0000s
-- execute("ALTER TABLE dast_site_profiles\nDROP CONSTRAINT IF EXISTS check_af44f54c96\n")
   -> 0.0028s
== 20220331174459 AddTextLimitToSubmitFieldDastSiteProfiles: reverted (0.0249s)

== 20220331174026 AddSubmitFieldToDastSiteProfiles: reverting =================
-- remove_column(:dast_site_profiles, :auth_submit_field, :text)
   -> 0.0050s
== 20220331174026 AddSubmitFieldToDastSiteProfiles: reverted (0.0095s) ========

Related to #355526 (closed)